feature: Add inline replies (#1659)

* Add inline replies

* Missed a few things

* Change xml docs, IUserMessage, and other changes

* Missed one when changing

* Fix referencedMessage author

src/Discord.Net.Commands/ModuleBase.cs

@@ -35,9 +35,10 @@ namespace Discord.Commands
         ///     Specifies if notifications are sent for mentioned users and roles in the <paramref name="message"/>.
         ///     If <c>null</c>, all mentioned roles and users will be notified.
         /// </param>
-        protected virtual async Task<IUserMessage> ReplyAsync(string message = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null)
+        /// <param name="messageReference">The message references to be included. Used to reply to specific messages.</param>
+        protected virtual async Task<IUserMessage> ReplyAsync(string message = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
         {
-            return await Context.Channel.SendMessageAsync(message, isTTS, embed, options, allowedMentions).ConfigureAwait(false);
+            return await Context.Channel.SendMessageAsync(message, isTTS, embed, options, allowedMentions, messageReference).ConfigureAwait(false);
         }
         /// <summary>
         ///     The method to execute before executing the command.

src/Discord.Net.Core/Entities/Channels/IMessageChannel.cs

@@ -27,11 +27,12 @@ namespace Discord
         ///     Specifies if notifications are sent for mentioned users and roles in the message <paramref name="text"/>.
         ///     If <c>null</c>, all mentioned roles and users will be notified.
         /// </param>
+        /// <param name="messageReference">The message references to be included. Used to reply to specific messages.</param>
         /// <returns>
         ///     A task that represents an asynchronous send operation for delivering the message. The task result
         ///     contains the sent message.
         /// </returns>
-        Task<IUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null);
+        Task<IUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null, MessageReference messageReference = null);
         /// <summary>
         ///     Sends a file to this message channel with an optional caption.
         /// </summary>
@@ -63,11 +64,12 @@ namespace Discord
         ///     Specifies if notifications are sent for mentioned users and roles in the message <paramref name="text"/>.
         ///     If <c>null</c>, all mentioned roles and users will be notified.
         /// </param>
+        /// <param name="messageReference">The message references to be included. Used to reply to specific messages.</param>
         /// <returns>
         ///     A task that represents an asynchronous send operation for delivering the message. The task result
         ///     contains the sent message.
         /// </returns>
-        Task<IUserMessage> SendFileAsync(string filePath, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null);
+        Task<IUserMessage> SendFileAsync(string filePath, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null);
         /// <summary>
         ///     Sends a file to this message channel with an optional caption.
         /// </summary>
@@ -96,11 +98,12 @@ namespace Discord
         ///     Specifies if notifications are sent for mentioned users and roles in the message <paramref name="text"/>.
         ///     If <c>null</c>, all mentioned roles and users will be notified.
         /// </param>
+        /// <param name="messageReference">The message references to be included. Used to reply to specific messages.</param>
         /// <returns>
         ///     A task that represents an asynchronous send operation for delivering the message. The task result
         ///     contains the sent message.
         /// </returns>
-        Task<IUserMessage> SendFileAsync(Stream stream, string filename, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null);
+        Task<IUserMessage> SendFileAsync(Stream stream, string filename, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null);
 
         /// <summary>
         ///     Gets a message from this message channel.

src/Discord.Net.Core/Entities/Messages/AllowedMentions.cs

@@ -49,6 +49,14 @@ namespace Discord
         /// </summary>
         public List<ulong> UserIds { get; set; } = new List<ulong>();
 
+        /// <summary>
+        ///     Gets or sets whether to mention the author of the message you are replying to or not.
+        /// </summary>
+        /// <remarks>
+        ///     Specifically for inline replies.
+        /// </remarks>
+        public bool? MentionRepliedUser { get; set; } = null;
+
         /// <summary>
         ///     Initializes a new instance of the <see cref="AllowedMentions"/> class.
         /// </summary>

src/Discord.Net.Core/Entities/Messages/IMessage.cs

@@ -148,11 +148,11 @@ namespace Discord
         MessageApplication Application { get; }
 
         /// <summary>
-        ///     Gets the reference to the original message if it was crossposted.
+        ///     Gets the reference to the original message if it is a crosspost, channel follow add, pin, or reply message.
         /// </summary>
         /// <remarks>
-        ///     Sent with Cross-posted messages, meaning they were published from news channels
-        ///     and received by subscriber channels.
+        ///     Sent with cross-posted messages, meaning they were published from news channels
+        ///     and received by subscriber channels, channel follow adds, pins, and message replies.
         /// </remarks>
         /// <returns>
         ///     A message's reference, if any is associated.

src/Discord.Net.Core/Entities/Messages/IUserMessage.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Collections.Generic;
 using System.Threading.Tasks;
 
 namespace Discord
@@ -9,6 +8,14 @@ namespace Discord
     /// </summary>
     public interface IUserMessage : IMessage
     {
+        /// <summary>
+        ///     Gets the referenced message if it is a crosspost, channel follow add, pin, or reply message.
+        /// </summary>
+        /// <returns>
+        ///     The referenced message, if any is associated and still exists.
+        /// </returns>
+        IUserMessage ReferencedMessage { get; }
+
         /// <summary>
         ///     Modifies this message.
         /// </summary>

src/Discord.Net.Core/Entities/Messages/MessageReference.cs

@@ -3,7 +3,7 @@ using System.Diagnostics;
 namespace Discord
 {
     /// <summary>
-    ///     Contains the IDs sent from a crossposted message.
+    ///     Contains the IDs sent from a crossposted message or inline reply.
     /// </summary>
     [DebuggerDisplay(@"{DebuggerDisplay,nq}")]
     public class MessageReference
@@ -16,13 +16,36 @@ namespace Discord
         /// <summary>
         ///     Gets the Channel ID of the original message.
         /// </summary>
-        public ulong ChannelId { get; internal set; }
+        /// <remarks>
+        ///     It only will be the default value (zero) if it was instantiated with a <see langword="null"/> in the constructor.
+        /// </remarks>
+        public ulong ChannelId { get => InternalChannelId.GetValueOrDefault(); }
+        internal Optional<ulong> InternalChannelId;
 
         /// <summary>
         ///     Gets the Guild ID of the original message.
         /// </summary>
         public Optional<ulong> GuildId { get; internal set; }
 
+        /// <summary>
+        ///     Initializes a new instance of the <see cref="MessageReference"/> class.
+        /// </summary>
+        /// <param name="messageId">
+        ///     The ID of the message that will be referenced. Used to reply to specific messages and the only parameter required for it.
+        /// </param>
+        /// <param name="channelId">
+        ///     The ID of the channel that will be referenced. It will be validated if sent.
+        /// </param>
+        /// <param name="guildId">
+        ///     The ID of the guild that will be referenced. It will be validated if sent.
+        /// </param>
+        public MessageReference(ulong? messageId = null, ulong? channelId = null, ulong? guildId = null)
+        {
+            MessageId = messageId ?? Optional.Create<ulong>();
+            InternalChannelId = channelId ?? Optional.Create<ulong>();
+            GuildId = guildId ?? Optional.Create<ulong>();
+        }
+
         private string DebuggerDisplay
             => $"Channel ID: ({ChannelId}){(GuildId.IsSpecified ? $", Guild ID: ({GuildId.Value})" : "")}" +
             $"{(MessageId.IsSpecified ? $", Message ID: ({MessageId.Value})" : "")}";

src/Discord.Net.Core/Entities/Messages/MessageType.cs

@@ -57,5 +57,12 @@ namespace Discord
         ///     The message for when a news channel subscription is added to a text channel.
         /// </summary>
         ChannelFollowAdd = 12,
+        /// <summary>
+        ///     The message is an inline reply.
+        /// </summary>
+        /// <remarks>
+        ///     Only available in API v8.
+        /// </remarks>
+        Reply = 19,
     }
 }

src/Discord.Net.Core/Entities/Users/IGuildUser.cs

@@ -73,7 +73,7 @@ namespace Discord
         /// </summary>
         /// <example>
         ///     <para>The following example checks if the current user has the ability to send a message with attachment in
-        ///     this channel; if so, uploads a file via <see cref="IMessageChannel.SendFileAsync(string, string, bool, Embed, RequestOptions, bool, AllowedMentions)"/>.</para>
+        ///     this channel; if so, uploads a file via <see cref="IMessageChannel.SendFileAsync(string, string, bool, Embed, RequestOptions, bool, AllowedMentions, MessageReference)"/>.</para>
         ///     <code language="cs">
         ///     if (currentUser?.GetPermissions(targetChannel)?.AttachFiles)
         ///         await targetChannel.SendFileAsync("fortnite.png");

src/Discord.Net.Core/Extensions/MessageExtensions.cs

@@ -71,5 +71,25 @@ namespace Discord
             foreach (var rxn in reactions)
                 await msg.RemoveReactionAsync(rxn, user, options).ConfigureAwait(false);
         }
+
+        /// <summary>
+        ///     Sends an inline reply that references a message.
+        /// </summary>
+        /// <param name="text">The message to be sent.</param>
+        /// <param name="isTTS">Determines whether the message should be read aloud by Discord or not.</param>
+        /// <param name="embed">The <see cref="Discord.EmbedType.Rich"/> <see cref="Embed"/> to be sent.</param>
+        /// <param name="allowedMentions">
+        ///     Specifies if notifications are sent for mentioned users and roles in the message <paramref name="text"/>.
+        ///     If <c>null</c>, all mentioned roles and users will be notified.
+        /// </param>
+        /// <param name="options">The options to be used when sending the request.</param>
+        /// <returns>
+        ///     A task that represents an asynchronous send operation for delivering the message. The task result
+        ///     contains the sent message.
+        /// </returns>
+        public static async Task<IUserMessage> ReplyAsync(this IUserMessage msg, string text = null, bool isTTS = false, Embed embed = null, AllowedMentions allowedMentions = null, RequestOptions options = null)
+        {
+            return await msg.Channel.SendMessageAsync(text, isTTS, embed, options, allowedMentions, new MessageReference(messageId: msg.Id)).ConfigureAwait(false);
+        }
     }
 }

src/Discord.Net.Rest/API/Common/Message.cs

@@ -56,5 +56,7 @@ namespace Discord.API
         public Optional<MessageFlags> Flags { get; set; }
         [JsonProperty("allowed_mentions")]
         public Optional<AllowedMentions> AllowedMentions { get; set; }
+        [JsonProperty("referenced_message")]
+        public Optional<Message> ReferencedMessage { get; set; }
     }
 }

src/Discord.Net.Rest/API/Common/MessageReference.cs

@@ -8,7 +8,7 @@ namespace Discord.API
         public Optional<ulong> MessageId { get; set; }
 
         [JsonProperty("channel_id")]
-        public ulong ChannelId { get; set; }
+        public Optional<ulong> ChannelId { get; set; } // Optional when sending, always present when receiving
 
         [JsonProperty("guild_id")]
         public Optional<ulong> GuildId { get; set; }

src/Discord.Net.Rest/API/Rest/CreateMessageParams.cs

@@ -17,6 +17,8 @@ namespace Discord.API.Rest
         public Optional<Embed> Embed { get; set; }
         [JsonProperty("allowed_mentions")]
         public Optional<AllowedMentions> AllowedMentions { get; set; }
+        [JsonProperty("message_reference")]
+        public Optional<MessageReference> MessageReference { get; set; }
 
         public CreateMessageParams(string content)
         {

src/Discord.Net.Rest/API/Rest/UploadFileParams.cs

@@ -20,6 +20,7 @@ namespace Discord.API.Rest
         public Optional<bool> IsTTS { get; set; }
         public Optional<Embed> Embed { get; set; }
         public Optional<AllowedMentions> AllowedMentions { get; set; }
+        public Optional<MessageReference> MessageReference { get; set; }
         public bool IsSpoiler { get; set; } = false;
 
         public UploadFileParams(Stream file)

src/Discord.Net.Rest/Entities/Channels/ChannelHelper.cs

@@ -6,7 +6,6 @@ using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
 using Model = Discord.API.Channel;
-using UserModel = Discord.API.User;
 
 namespace Discord.Rest
 {
@@ -130,7 +129,7 @@ namespace Discord.Rest
             var model = await client.ApiClient.GetChannelMessageAsync(channel.Id, id, options).ConfigureAwait(false);
             if (model == null)
                 return null;
-            var author = GetAuthor(client, guild, model.Author.Value, model.WebhookId.ToNullable());
+            var author = MessageHelper.GetAuthor(client, guild, model.Author.Value, model.WebhookId.ToNullable());
             return RestMessage.Create(client, channel, author, model);
         }
         public static IAsyncEnumerable<IReadOnlyCollection<RestMessage>> GetMessagesAsync(IMessageChannel channel, BaseDiscordClient client,
@@ -165,7 +164,7 @@ namespace Discord.Rest
                     var builder = ImmutableArray.CreateBuilder<RestMessage>();
                     foreach (var model in models)
                     {
-                        var author = GetAuthor(client, guild, model.Author.Value, model.WebhookId.ToNullable());
+                        var author = MessageHelper.GetAuthor(client, guild, model.Author.Value, model.WebhookId.ToNullable());
                         builder.Add(RestMessage.Create(client, channel, author, model));
                     }
                     return builder.ToImmutable();
@@ -193,7 +192,7 @@ namespace Discord.Rest
             var builder = ImmutableArray.CreateBuilder<RestMessage>();
             foreach (var model in models)
             {
-                var author = GetAuthor(client, guild, model.Author.Value, model.WebhookId.ToNullable());
+                var author = MessageHelper.GetAuthor(client, guild, model.Author.Value, model.WebhookId.ToNullable());
                 builder.Add(RestMessage.Create(client, channel, author, model));
             }
             return builder.ToImmutable();
@@ -201,7 +200,7 @@ namespace Discord.Rest
 
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
         public static async Task<RestUserMessage> SendMessageAsync(IMessageChannel channel, BaseDiscordClient client,
-            string text, bool isTTS, Embed embed, AllowedMentions allowedMentions, RequestOptions options)
+            string text, bool isTTS, Embed embed, AllowedMentions allowedMentions, MessageReference messageReference, RequestOptions options)
         {
             Preconditions.AtMost(allowedMentions?.RoleIds?.Count ?? 0, 100, nameof(allowedMentions.RoleIds), "A max of 100 role Ids are allowed.");
             Preconditions.AtMost(allowedMentions?.UserIds?.Count ?? 0, 100, nameof(allowedMentions.UserIds), "A max of 100 user Ids are allowed.");
@@ -222,7 +221,7 @@ namespace Discord.Rest
                 }
             }
 
-            var args = new CreateMessageParams(text) { IsTTS = isTTS, Embed = embed?.ToModel(), AllowedMentions = allowedMentions?.ToModel() };
+            var args = new CreateMessageParams(text) { IsTTS = isTTS, Embed = embed?.ToModel(), AllowedMentions = allowedMentions?.ToModel(), MessageReference = messageReference?.ToModel() };
             var model = await client.ApiClient.CreateMessageAsync(channel.Id, args, options).ConfigureAwait(false);
             return RestUserMessage.Create(client, channel, client.CurrentUser, model);
         }
@@ -252,16 +251,16 @@ namespace Discord.Rest
         /// <exception cref="IOException">An I/O error occurred while opening the file.</exception>
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
         public static async Task<RestUserMessage> SendFileAsync(IMessageChannel channel, BaseDiscordClient client,
-            string filePath, string text, bool isTTS, Embed embed, AllowedMentions allowedMentions, RequestOptions options, bool isSpoiler)
+            string filePath, string text, bool isTTS, Embed embed, AllowedMentions allowedMentions, MessageReference messageReference, RequestOptions options, bool isSpoiler)
         {
             string filename = Path.GetFileName(filePath);
             using (var file = File.OpenRead(filePath))
-                return await SendFileAsync(channel, client, file, filename, text, isTTS, embed, allowedMentions, options, isSpoiler).ConfigureAwait(false);
+                return await SendFileAsync(channel, client, file, filename, text, isTTS, embed, allowedMentions, messageReference, options, isSpoiler).ConfigureAwait(false);
         }
 
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
         public static async Task<RestUserMessage> SendFileAsync(IMessageChannel channel, BaseDiscordClient client,
-            Stream stream, string filename, string text, bool isTTS, Embed embed, AllowedMentions allowedMentions, RequestOptions options, bool isSpoiler)
+            Stream stream, string filename, string text, bool isTTS, Embed embed, AllowedMentions allowedMentions, MessageReference messageReference, RequestOptions options, bool isSpoiler)
         {
             Preconditions.AtMost(allowedMentions?.RoleIds?.Count ?? 0, 100, nameof(allowedMentions.RoleIds), "A max of 100 role Ids are allowed.");
             Preconditions.AtMost(allowedMentions?.UserIds?.Count ?? 0, 100, nameof(allowedMentions.UserIds), "A max of 100 user Ids are allowed.");
@@ -282,7 +281,7 @@ namespace Discord.Rest
                 }
             }
 
-            var args = new UploadFileParams(stream) { Filename = filename, Content = text, IsTTS = isTTS, Embed = embed?.ToModel() ?? Optional<API.Embed>.Unspecified, AllowedMentions = allowedMentions?.ToModel() ?? Optional<API.AllowedMentions>.Unspecified, IsSpoiler = isSpoiler };
+            var args = new UploadFileParams(stream) { Filename = filename, Content = text, IsTTS = isTTS, Embed = embed?.ToModel() ?? Optional<API.Embed>.Unspecified, AllowedMentions = allowedMentions?.ToModel() ?? Optional<API.AllowedMentions>.Unspecified, MessageReference = messageReference?.ToModel() ?? Optional<API.MessageReference>.Unspecified, IsSpoiler = isSpoiler };
             var model = await client.ApiClient.UploadFileAsync(channel.Id, args, options).ConfigureAwait(false);
             return RestUserMessage.Create(client, channel, client.CurrentUser, model);
         }
@@ -450,16 +449,5 @@ namespace Discord.Rest
             };
             await client.ApiClient.ModifyGuildChannelAsync(channel.Id, apiArgs, options).ConfigureAwait(false);
         }
-
-        //Helpers
-        private static IUser GetAuthor(BaseDiscordClient client, IGuild guild, UserModel model, ulong? webhookId)
-        {
-            IUser author = null;
-            if (guild != null)
-                author = guild.GetUserAsync(model.Id, CacheMode.CacheOnly).Result;
-            if (author == null)
-                author = RestUser.Create(client, guild, model, webhookId);
-            return author;
-        }
     }
 }

src/Discord.Net.Rest/Entities/Channels/IRestMessageChannel.cs

@@ -24,17 +24,18 @@ namespace Discord.Rest
         ///     Specifies if notifications are sent for mentioned users and roles in the message <paramref name="text"/>.
         ///     If <c>null</c>, all mentioned roles and users will be notified.
         /// </param>
+        /// <param name="messageReference">The message references to be included. Used to reply to specific messages.</param>
         /// <returns>
         ///     A task that represents an asynchronous send operation for delivering the message. The task result
         ///     contains the sent message.
         /// </returns>
-        new Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null);
+        new Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null, MessageReference messageReference = null);
         /// <summary>
         ///     Sends a file to this message channel with an optional caption.
         /// </summary>
         /// <remarks>
         ///     This method follows the same behavior as described in 
-        ///     <see cref="IMessageChannel.SendFileAsync(string, string, bool, Embed, RequestOptions, bool, AllowedMentions)"/>. Please visit
+        ///     <see cref="IMessageChannel.SendFileAsync(string, string, bool, Embed, RequestOptions, bool, AllowedMentions, MessageReference)"/>. Please visit
         ///     its documentation for more details on this method.
         /// </remarks>
         /// <param name="filePath">The file path of the file.</param>
@@ -47,16 +48,17 @@ namespace Discord.Rest
         ///     Specifies if notifications are sent for mentioned users and roles in the message <paramref name="text"/>.
         ///     If <c>null</c>, all mentioned roles and users will be notified.
         /// </param>
+        /// <param name="messageReference">The message references to be included. Used to reply to specific messages.</param>
         /// <returns>
         ///     A task that represents an asynchronous send operation for delivering the message. The task result
         ///     contains the sent message.
         /// </returns>
-        new Task<RestUserMessage> SendFileAsync(string filePath, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null);
+        new Task<RestUserMessage> SendFileAsync(string filePath, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null);
         /// <summary>
         ///     Sends a file to this message channel with an optional caption.
         /// </summary>
         /// <remarks>
-        ///     This method follows the same behavior as described in <see cref="IMessageChannel.SendFileAsync(Stream, string, string, bool, Embed, RequestOptions, bool, AllowedMentions)"/>.
+        ///     This method follows the same behavior as described in <see cref="IMessageChannel.SendFileAsync(Stream, string, string, bool, Embed, RequestOptions, bool, AllowedMentions, MessageReference)"/>.
         ///     Please visit its documentation for more details on this method.
         /// </remarks>
         /// <param name="stream">The <see cref="Stream" /> of the file to be sent.</param>
@@ -70,11 +72,12 @@ namespace Discord.Rest
         ///     Specifies if notifications are sent for mentioned users and roles in the message <paramref name="text"/>.
         ///     If <c>null</c>, all mentioned roles and users will be notified.
         /// </param>
+        /// <param name="messageReference">The message references to be included. Used to reply to specific messages.</param>
         /// <returns>
         ///     A task that represents an asynchronous send operation for delivering the message. The task result
         ///     contains the sent message.
         /// </returns>
-        new Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null);
+        new Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null);
 
         /// <summary>
         ///     Gets a message from this message channel.

src/Discord.Net.Rest/Entities/Channels/RestDMChannel.cs

@@ -93,8 +93,8 @@ namespace Discord.Rest
 
         /// <inheritdoc />
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
-        public Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendMessageAsync(this, Discord, text, isTTS, embed, allowedMentions, options);
+        public Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendMessageAsync(this, Discord, text, isTTS, embed, allowedMentions, messageReference, options);
 
         /// <inheritdoc />
         /// <exception cref="ArgumentException">
@@ -121,12 +121,12 @@ namespace Discord.Rest
         /// <exception cref="NotSupportedException"><paramref name="filePath" /> is in an invalid format.</exception>
         /// <exception cref="IOException">An I/O error occurred while opening the file.</exception>
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
-        public Task<RestUserMessage> SendFileAsync(string filePath, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendFileAsync(this, Discord, filePath, text, isTTS, embed, allowedMentions, options, isSpoiler);
+        public Task<RestUserMessage> SendFileAsync(string filePath, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendFileAsync(this, Discord, filePath, text, isTTS, embed, allowedMentions, messageReference, options, isSpoiler);
         /// <inheritdoc />
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
-        public Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendFileAsync(this, Discord, stream, filename, text, isTTS, embed, allowedMentions, options, isSpoiler);
+        public Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendFileAsync(this, Discord, stream, filename, text, isTTS, embed, allowedMentions, messageReference, options, isSpoiler);
 
         /// <inheritdoc />
         public Task DeleteMessageAsync(ulong messageId, RequestOptions options = null)
@@ -200,14 +200,14 @@ namespace Discord.Rest
         async Task<IReadOnlyCollection<IMessage>> IMessageChannel.GetPinnedMessagesAsync(RequestOptions options)
             => await GetPinnedMessagesAsync(options).ConfigureAwait(false);
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendFileAsync(string filePath, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions)
-            => await SendFileAsync(filePath, text, isTTS, embed, options, isSpoiler, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendFileAsync(string filePath, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendFileAsync(filePath, text, isTTS, embed, options, isSpoiler, allowedMentions, messageReference).ConfigureAwait(false);
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendFileAsync(Stream stream, string filename, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions)
-            => await SendFileAsync(stream, filename, text, isTTS, embed, options, isSpoiler, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendFileAsync(Stream stream, string filename, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendFileAsync(stream, filename, text, isTTS, embed, options, isSpoiler, allowedMentions, messageReference).ConfigureAwait(false);
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendMessageAsync(string text, bool isTTS, Embed embed, RequestOptions options, AllowedMentions allowedMentions)
-            => await SendMessageAsync(text, isTTS, embed, options, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendMessageAsync(string text, bool isTTS, Embed embed, RequestOptions options, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendMessageAsync(text, isTTS, embed, options, allowedMentions, messageReference).ConfigureAwait(false);
 
         //IChannel
         /// <inheritdoc />

src/Discord.Net.Rest/Entities/Channels/RestGroupChannel.cs

@@ -95,8 +95,8 @@ namespace Discord.Rest
 
         /// <inheritdoc />
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
-        public Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendMessageAsync(this, Discord, text, isTTS, embed, allowedMentions, options);
+        public Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendMessageAsync(this, Discord, text, isTTS, embed, allowedMentions, messageReference, options);
 
         /// <inheritdoc />
         /// <exception cref="ArgumentException">
@@ -123,12 +123,12 @@ namespace Discord.Rest
         /// <exception cref="NotSupportedException"><paramref name="filePath" /> is in an invalid format.</exception>
         /// <exception cref="IOException">An I/O error occurred while opening the file.</exception>
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
-        public Task<RestUserMessage> SendFileAsync(string filePath, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendFileAsync(this, Discord, filePath, text, isTTS, embed, allowedMentions, options, isSpoiler);
+        public Task<RestUserMessage> SendFileAsync(string filePath, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendFileAsync(this, Discord, filePath, text, isTTS, embed, allowedMentions, messageReference, options, isSpoiler);
         /// <inheritdoc />
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
-        public Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendFileAsync(this, Discord, stream, filename, text, isTTS, embed, allowedMentions, options, isSpoiler);
+        public Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendFileAsync(this, Discord, stream, filename, text, isTTS, embed, allowedMentions, messageReference, options, isSpoiler);
 
         /// <inheritdoc />
         public Task TriggerTypingAsync(RequestOptions options = null)
@@ -178,14 +178,14 @@ namespace Discord.Rest
         async Task<IReadOnlyCollection<IMessage>> IMessageChannel.GetPinnedMessagesAsync(RequestOptions options)
             => await GetPinnedMessagesAsync(options).ConfigureAwait(false);
 
-        async Task<IUserMessage> IMessageChannel.SendFileAsync(string filePath, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions)
-            => await SendFileAsync(filePath, text, isTTS, embed, options, isSpoiler, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendFileAsync(string filePath, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendFileAsync(filePath, text, isTTS, embed, options, isSpoiler, allowedMentions, messageReference).ConfigureAwait(false);
 
-        async Task<IUserMessage> IMessageChannel.SendFileAsync(Stream stream, string filename, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions)
-            => await SendFileAsync(stream, filename, text, isTTS, embed, options, isSpoiler, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendFileAsync(Stream stream, string filename, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendFileAsync(stream, filename, text, isTTS, embed, options, isSpoiler, allowedMentions, messageReference).ConfigureAwait(false);
 
-        async Task<IUserMessage> IMessageChannel.SendMessageAsync(string text, bool isTTS, Embed embed, RequestOptions options, AllowedMentions allowedMentions)
-            => await SendMessageAsync(text, isTTS, embed, options, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendMessageAsync(string text, bool isTTS, Embed embed, RequestOptions options, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendMessageAsync(text, isTTS, embed, options, allowedMentions, messageReference).ConfigureAwait(false);
 
         //IAudioChannel
         /// <inheritdoc />

src/Discord.Net.Rest/Entities/Channels/RestTextChannel.cs

@@ -102,8 +102,8 @@ namespace Discord.Rest
 
         /// <inheritdoc />
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
-        public Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendMessageAsync(this, Discord, text, isTTS, embed, allowedMentions, options);
+        public Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendMessageAsync(this, Discord, text, isTTS, embed, allowedMentions, messageReference, options);
 
         /// <inheritdoc />
         /// <exception cref="ArgumentException">
@@ -130,13 +130,13 @@ namespace Discord.Rest
         /// <exception cref="NotSupportedException"><paramref name="filePath" /> is in an invalid format.</exception>
         /// <exception cref="IOException">An I/O error occurred while opening the file.</exception>
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
-        public Task<RestUserMessage> SendFileAsync(string filePath, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendFileAsync(this, Discord, filePath, text, isTTS, embed, allowedMentions, options, isSpoiler);
+        public Task<RestUserMessage> SendFileAsync(string filePath, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendFileAsync(this, Discord, filePath, text, isTTS, embed, allowedMentions, messageReference, options, isSpoiler);
 
         /// <inheritdoc />
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
-        public Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendFileAsync(this, Discord, stream, filename, text, isTTS, embed, allowedMentions, options, isSpoiler);
+        public Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendFileAsync(this, Discord, stream, filename, text, isTTS, embed, allowedMentions, messageReference, options, isSpoiler);
 
         /// <inheritdoc />
         public Task DeleteMessageAsync(ulong messageId, RequestOptions options = null)
@@ -267,15 +267,15 @@ namespace Discord.Rest
             => await GetPinnedMessagesAsync(options).ConfigureAwait(false);
 
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendFileAsync(string filePath, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions)
-            => await SendFileAsync(filePath, text, isTTS, embed, options, isSpoiler, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendFileAsync(string filePath, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendFileAsync(filePath, text, isTTS, embed, options, isSpoiler, allowedMentions, messageReference).ConfigureAwait(false);
 
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendFileAsync(Stream stream, string filename, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions)
-            => await SendFileAsync(stream, filename, text, isTTS, embed, options, isSpoiler, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendFileAsync(Stream stream, string filename, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendFileAsync(stream, filename, text, isTTS, embed, options, isSpoiler, allowedMentions, messageReference).ConfigureAwait(false);
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendMessageAsync(string text, bool isTTS, Embed embed, RequestOptions options, AllowedMentions allowedMentions)
-            => await SendMessageAsync(text, isTTS, embed, options, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendMessageAsync(string text, bool isTTS, Embed embed, RequestOptions options, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendMessageAsync(text, isTTS, embed, options, allowedMentions, messageReference).ConfigureAwait(false);
 
         //IGuildChannel
         /// <inheritdoc />

src/Discord.Net.Rest/Entities/Messages/AllowedMentions.cs

@@ -11,5 +11,7 @@ namespace Discord.API
         public Optional<ulong[]> Roles { get; set; }
         [JsonProperty("users")]
         public Optional<ulong[]> Users { get; set; }
+        [JsonProperty("replied_user")]
+        public Optional<bool> RepliedUser { get; set; }
     }
 }

src/Discord.Net.Rest/Entities/Messages/MessageHelper.cs

@@ -6,6 +6,7 @@ using System.Linq;
 using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using Model = Discord.API.Message;
+using UserModel = Discord.API.User;
 
 namespace Discord.Rest
 {
@@ -290,7 +291,7 @@ namespace Discord.Rest
 
         public static MessageSource GetSource(Model msg)
         {
-            if (msg.Type != MessageType.Default)
+            if (msg.Type != MessageType.Default && msg.Type != MessageType.Reply)
                 return MessageSource.System;
             else if (msg.WebhookId.IsSpecified)
                 return MessageSource.Webhook;
@@ -307,5 +308,15 @@ namespace Discord.Rest
         {
             await client.ApiClient.CrosspostAsync(channelId, msgId, options).ConfigureAwait(false);
         }
+
+        public static IUser GetAuthor(BaseDiscordClient client, IGuild guild, UserModel model, ulong? webhookId)
+        {
+            IUser author = null;
+            if (guild != null)
+                author = guild.GetUserAsync(model.Id, CacheMode.CacheOnly).Result;
+            if (author == null)
+                author = RestUser.Create(client, guild, model, webhookId);
+            return author;
+        }
     }
 }

src/Discord.Net.Rest/Entities/Messages/RestMessage.cs

@@ -77,7 +77,7 @@ namespace Discord.Rest
         }
         internal static RestMessage Create(BaseDiscordClient discord, IMessageChannel channel, IUser author, Model model)
         {
-            if (model.Type == MessageType.Default)
+            if (model.Type == MessageType.Default || model.Type == MessageType.Reply)
                 return RestUserMessage.Create(discord, channel, author, model);
             else
                 return RestSystemMessage.Create(discord, channel, author, model);
@@ -119,7 +119,7 @@ namespace Discord.Rest
                 Reference = new MessageReference
                 {
                     GuildId = model.Reference.Value.GuildId,
-                    ChannelId = model.Reference.Value.ChannelId,
+                    InternalChannelId = model.Reference.Value.ChannelId,
                     MessageId = model.Reference.Value.MessageId
                 };
             }

src/Discord.Net.Rest/Entities/Messages/RestUserMessage.cs

@@ -15,6 +15,7 @@ namespace Discord.Rest
     {
         private bool _isMentioningEveryone, _isTTS, _isPinned, _isSuppressed;
         private long? _editedTimestampTicks;
+        private IUserMessage _referencedMessage;
         private ImmutableArray<Attachment> _attachments = ImmutableArray.Create<Attachment>();
         private ImmutableArray<Embed> _embeds = ImmutableArray.Create<Embed>();
         private ImmutableArray<ITag> _tags = ImmutableArray.Create<ITag>();
@@ -43,6 +44,8 @@ namespace Discord.Rest
         public override IReadOnlyCollection<RestUser> MentionedUsers => _userMentions;
         /// <inheritdoc />
         public override IReadOnlyCollection<ITag> Tags => _tags;
+        /// <inheritdoc />
+        public IUserMessage ReferencedMessage => _referencedMessage;
 
         internal RestUserMessage(BaseDiscordClient discord, ulong id, IMessageChannel channel, IUser author, MessageSource source)
             : base(discord, id, channel, author, source)
@@ -118,14 +121,21 @@ namespace Discord.Rest
                 }
             }
 
+            var guildId = (Channel as IGuildChannel)?.GuildId;
+            var guild = guildId != null ? (Discord as IDiscordClient).GetGuildAsync(guildId.Value, CacheMode.CacheOnly).Result : null;
             if (model.Content.IsSpecified)
             {
                 var text = model.Content.Value;
-                var guildId = (Channel as IGuildChannel)?.GuildId;
-                var guild = guildId != null ? (Discord as IDiscordClient).GetGuildAsync(guildId.Value, CacheMode.CacheOnly).Result : null;
                 _tags = MessageHelper.ParseTags(text, null, guild, _userMentions);
                 model.Content = text;
             }
+
+            if (model.ReferencedMessage.IsSpecified && model.ReferencedMessage.Value != null)
+            {
+                var refMsg = model.ReferencedMessage.Value;
+                IUser refMsgAuthor = MessageHelper.GetAuthor(Discord, guild, refMsg.Author.Value, refMsg.WebhookId.ToNullable());
+                _referencedMessage = RestUserMessage.Create(Discord, Channel, refMsgAuthor, refMsg);
+            }
         }
 
         /// <inheritdoc />

src/Discord.Net.Rest/Extensions/EntityExtensions.cs

@@ -68,6 +68,16 @@ namespace Discord.Rest
                 Parse = entity.AllowedTypes?.EnumerateMentionTypes().ToArray(),
                 Roles = entity.RoleIds?.ToArray(),
                 Users = entity.UserIds?.ToArray(),
+                RepliedUser = entity.MentionRepliedUser ?? Optional.Create<bool>(),
+            };
+        }
+        public static API.MessageReference ToModel(this MessageReference entity)
+        {
+            return new API.MessageReference()
+            {
+                ChannelId = entity.InternalChannelId,
+                GuildId = entity.GuildId,
+                MessageId = entity.MessageId,
             };
         }
         public static IEnumerable<string> EnumerateMentionTypes(this AllowedMentionTypes mentionTypes)

src/Discord.Net.WebSocket/Entities/Channels/ISocketMessageChannel.cs

@@ -33,16 +33,17 @@ namespace Discord.WebSocket
         ///     Specifies if notifications are sent for mentioned users and roles in the message <paramref name="text"/>.
         ///     If <c>null</c>, all mentioned roles and users will be notified.
         /// </param>
+        /// <param name="messageReference">The message references to be included. Used to reply to specific messages.</param>
         /// <returns>
         ///     A task that represents an asynchronous send operation for delivering the message. The task result
         ///     contains the sent message.
         /// </returns>
-        new Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null);
+        new Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null, MessageReference messageReference = null);
         /// <summary>
         ///     Sends a file to this message channel with an optional caption.
         /// </summary>
         /// <remarks>
-        ///     This method follows the same behavior as described in <see cref="IMessageChannel.SendFileAsync(string, string, bool, Embed, RequestOptions, bool, AllowedMentions)"/>.
+        ///     This method follows the same behavior as described in <see cref="IMessageChannel.SendFileAsync(string, string, bool, Embed, RequestOptions, bool, AllowedMentions, MessageReference)"/>.
         ///     Please visit its documentation for more details on this method.
         /// </remarks>
         /// <param name="filePath">The file path of the file.</param>
@@ -55,16 +56,17 @@ namespace Discord.WebSocket
         ///     Specifies if notifications are sent for mentioned users and roles in the message <paramref name="text"/>.
         ///     If <c>null</c>, all mentioned roles and users will be notified.
         /// </param>
+        /// <param name="messageReference">The message references to be included. Used to reply to specific messages.</param>
         /// <returns>
         ///     A task that represents an asynchronous send operation for delivering the message. The task result
         ///     contains the sent message.
         /// </returns>
-        new Task<RestUserMessage> SendFileAsync(string filePath, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null);
+        new Task<RestUserMessage> SendFileAsync(string filePath, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null);
         /// <summary>
         ///     Sends a file to this message channel with an optional caption.
         /// </summary>
         /// <remarks>
-        ///     This method follows the same behavior as described in <see cref="IMessageChannel.SendFileAsync(Stream, string, string, bool, Embed, RequestOptions, bool, AllowedMentions)"/>.
+        ///     This method follows the same behavior as described in <see cref="IMessageChannel.SendFileAsync(Stream, string, string, bool, Embed, RequestOptions, bool, AllowedMentions, MessageReference)"/>.
         ///     Please visit its documentation for more details on this method.
         /// </remarks>
         /// <param name="stream">The <see cref="Stream" /> of the file to be sent.</param>
@@ -78,11 +80,12 @@ namespace Discord.WebSocket
         ///     Specifies if notifications are sent for mentioned users and roles in the message <paramref name="text"/>.
         ///     If <c>null</c>, all mentioned roles and users will be notified.
         /// </param>
+        /// <param name="messageReference">The message references to be included. Used to reply to specific messages.</param>
         /// <returns>
         ///     A task that represents an asynchronous send operation for delivering the message. The task result
         ///     contains the sent message.
         /// </returns>
-        new Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null);
+        new Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null);
 
         /// <summary>
         ///     Gets a cached message from this channel.

src/Discord.Net.WebSocket/Entities/Channels/SocketDMChannel.cs

@@ -135,16 +135,16 @@ namespace Discord.WebSocket
 
         /// <inheritdoc />
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
-        public Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendMessageAsync(this, Discord, text, isTTS, embed, allowedMentions, options);
+        public Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendMessageAsync(this, Discord, text, isTTS, embed, allowedMentions, messageReference, options);
 
         /// <inheritdoc />
-        public Task<RestUserMessage> SendFileAsync(string filePath, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendFileAsync(this, Discord, filePath, text, isTTS, embed, allowedMentions, options, isSpoiler);
+        public Task<RestUserMessage> SendFileAsync(string filePath, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendFileAsync(this, Discord, filePath, text, isTTS, embed, allowedMentions, messageReference, options, isSpoiler);
         /// <inheritdoc />
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
-        public Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendFileAsync(this, Discord, stream, filename, text, isTTS, embed, allowedMentions, options, isSpoiler);
+        public Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendFileAsync(this, Discord, stream, filename, text, isTTS, embed, allowedMentions, messageReference, options, isSpoiler);
         /// <inheritdoc />
         public Task DeleteMessageAsync(ulong messageId, RequestOptions options = null)
             => ChannelHelper.DeleteMessageAsync(this, messageId, Discord, options);
@@ -229,14 +229,14 @@ namespace Discord.WebSocket
         async Task<IReadOnlyCollection<IMessage>> IMessageChannel.GetPinnedMessagesAsync(RequestOptions options)
             => await GetPinnedMessagesAsync(options).ConfigureAwait(false);
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendFileAsync(string filePath, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions)
-            => await SendFileAsync(filePath, text, isTTS, embed, options, isSpoiler, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendFileAsync(string filePath, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendFileAsync(filePath, text, isTTS, embed, options, isSpoiler, allowedMentions, messageReference).ConfigureAwait(false);
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendFileAsync(Stream stream, string filename, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions)
-            => await SendFileAsync(stream, filename, text, isTTS, embed, options, isSpoiler, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendFileAsync(Stream stream, string filename, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendFileAsync(stream, filename, text, isTTS, embed, options, isSpoiler, allowedMentions, messageReference).ConfigureAwait(false);
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendMessageAsync(string text, bool isTTS, Embed embed, RequestOptions options, AllowedMentions allowedMentions)
-            => await SendMessageAsync(text, isTTS, embed, options, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendMessageAsync(string text, bool isTTS, Embed embed, RequestOptions options, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendMessageAsync(text, isTTS, embed, options, allowedMentions, messageReference).ConfigureAwait(false);
 
         //IChannel
         /// <inheritdoc />

src/Discord.Net.WebSocket/Entities/Channels/SocketGroupChannel.cs

@@ -163,15 +163,15 @@ namespace Discord.WebSocket
 
         /// <inheritdoc />
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
-        public Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendMessageAsync(this, Discord, text, isTTS, embed, allowedMentions, options);
+        public Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendMessageAsync(this, Discord, text, isTTS, embed, allowedMentions, messageReference, options);
 
         /// <inheritdoc />
-        public Task<RestUserMessage> SendFileAsync(string filePath, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendFileAsync(this, Discord, filePath, text, isTTS, embed, allowedMentions, options, isSpoiler);
+        public Task<RestUserMessage> SendFileAsync(string filePath, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendFileAsync(this, Discord, filePath, text, isTTS, embed, allowedMentions, messageReference, options, isSpoiler);
         /// <inheritdoc />
-        public Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendFileAsync(this, Discord, stream, filename, text, isTTS, embed, allowedMentions, options, isSpoiler);
+        public Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendFileAsync(this, Discord, stream, filename, text, isTTS, embed, allowedMentions, messageReference, options, isSpoiler);
 
         /// <inheritdoc />
         public Task DeleteMessageAsync(ulong messageId, RequestOptions options = null)
@@ -293,14 +293,14 @@ namespace Discord.WebSocket
             => await GetPinnedMessagesAsync(options).ConfigureAwait(false);
 
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendFileAsync(string filePath, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions)
-            => await SendFileAsync(filePath, text, isTTS, embed, options, isSpoiler, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendFileAsync(string filePath, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendFileAsync(filePath, text, isTTS, embed, options, isSpoiler, allowedMentions, messageReference).ConfigureAwait(false);
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendFileAsync(Stream stream, string filename, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions)
-            => await SendFileAsync(stream, filename, text, isTTS, embed, options, isSpoiler, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendFileAsync(Stream stream, string filename, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendFileAsync(stream, filename, text, isTTS, embed, options, isSpoiler, allowedMentions, messageReference).ConfigureAwait(false);
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendMessageAsync(string text, bool isTTS, Embed embed, RequestOptions options, AllowedMentions allowedMentions)
-            => await SendMessageAsync(text, isTTS, embed, options, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendMessageAsync(string text, bool isTTS, Embed embed, RequestOptions options, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendMessageAsync(text, isTTS, embed, options, allowedMentions, messageReference).ConfigureAwait(false);
 
         //IAudioChannel
         /// <inheritdoc />

src/Discord.Net.WebSocket/Entities/Channels/SocketTextChannel.cs

@@ -161,17 +161,17 @@ namespace Discord.WebSocket
 
         /// <inheritdoc />
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
-        public Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendMessageAsync(this, Discord, text, isTTS, embed, allowedMentions, options);
+        public Task<RestUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendMessageAsync(this, Discord, text, isTTS, embed, allowedMentions, messageReference, options);
 
         /// <inheritdoc />
-        public Task<RestUserMessage> SendFileAsync(string filePath, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendFileAsync(this, Discord, filePath, text, isTTS, embed, allowedMentions, options, isSpoiler);
+        public Task<RestUserMessage> SendFileAsync(string filePath, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendFileAsync(this, Discord, filePath, text, isTTS, embed, allowedMentions, messageReference, options, isSpoiler);
 
         /// <inheritdoc />
         /// <exception cref="ArgumentOutOfRangeException">Message content is too long, length must be less or equal to <see cref="DiscordConfig.MaxMessageSize"/>.</exception>
-        public Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
-            => ChannelHelper.SendFileAsync(this, Discord, stream, filename, text, isTTS, embed, allowedMentions, options, isSpoiler);
+        public Task<RestUserMessage> SendFileAsync(Stream stream, string filename, string text, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
+            => ChannelHelper.SendFileAsync(this, Discord, stream, filename, text, isTTS, embed, allowedMentions, messageReference, options, isSpoiler);
 
         /// <inheritdoc />
         public Task DeleteMessagesAsync(IEnumerable<IMessage> messages, RequestOptions options = null)
@@ -302,14 +302,14 @@ namespace Discord.WebSocket
             => await GetPinnedMessagesAsync(options).ConfigureAwait(false);
 
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendFileAsync(string filePath, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions)
-            => await SendFileAsync(filePath, text, isTTS, embed, options, isSpoiler, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendFileAsync(string filePath, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendFileAsync(filePath, text, isTTS, embed, options, isSpoiler, allowedMentions, messageReference).ConfigureAwait(false);
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendFileAsync(Stream stream, string filename, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions)
-            => await SendFileAsync(stream, filename, text, isTTS, embed, options, isSpoiler, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendFileAsync(Stream stream, string filename, string text, bool isTTS, Embed embed, RequestOptions options, bool isSpoiler, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendFileAsync(stream, filename, text, isTTS, embed, options, isSpoiler, allowedMentions, messageReference).ConfigureAwait(false);
         /// <inheritdoc />
-        async Task<IUserMessage> IMessageChannel.SendMessageAsync(string text, bool isTTS, Embed embed, RequestOptions options, AllowedMentions allowedMentions)
-            => await SendMessageAsync(text, isTTS, embed, options, allowedMentions).ConfigureAwait(false);
+        async Task<IUserMessage> IMessageChannel.SendMessageAsync(string text, bool isTTS, Embed embed, RequestOptions options, AllowedMentions allowedMentions, MessageReference messageReference)
+            => await SendMessageAsync(text, isTTS, embed, options, allowedMentions, messageReference).ConfigureAwait(false);
 
         // INestedChannel
         /// <inheritdoc />

src/Discord.Net.WebSocket/Entities/Messages/SocketMessage.cs

@@ -110,7 +110,7 @@ namespace Discord.WebSocket
         }
         internal static SocketMessage Create(DiscordSocketClient discord, ClientState state, SocketUser author, ISocketMessageChannel channel, Model model)
         {
-            if (model.Type == MessageType.Default)
+            if (model.Type == MessageType.Default || model.Type == MessageType.Reply)
                 return SocketUserMessage.Create(discord, state, author, channel, model);
             else
                 return SocketSystemMessage.Create(discord, state, author, channel, model);
@@ -152,7 +152,7 @@ namespace Discord.WebSocket
                 Reference = new MessageReference
                 {
                     GuildId = model.Reference.Value.GuildId,
-                    ChannelId = model.Reference.Value.ChannelId,
+                    InternalChannelId = model.Reference.Value.ChannelId,
                     MessageId = model.Reference.Value.MessageId
                 };
             }

src/Discord.Net.WebSocket/Entities/Messages/SocketUserMessage.cs

@@ -17,6 +17,7 @@ namespace Discord.WebSocket
     {
         private bool _isMentioningEveryone, _isTTS, _isPinned, _isSuppressed;
         private long? _editedTimestampTicks;
+        private IUserMessage _referencedMessage;
         private ImmutableArray<Attachment> _attachments = ImmutableArray.Create<Attachment>();
         private ImmutableArray<Embed> _embeds = ImmutableArray.Create<Embed>();
         private ImmutableArray<ITag> _tags = ImmutableArray.Create<ITag>();
@@ -45,6 +46,8 @@ namespace Discord.WebSocket
         public override IReadOnlyCollection<SocketRole> MentionedRoles => _roleMentions;
         /// <inheritdoc />
         public override IReadOnlyCollection<SocketUser> MentionedUsers => _userMentions;
+        /// <inheritdoc />
+        public IUserMessage ReferencedMessage => _referencedMessage;
 
         internal SocketUserMessage(DiscordSocketClient discord, ulong id, ISocketMessageChannel channel, SocketUser author, MessageSource source)
             : base(discord, id, channel, author, source)
@@ -131,6 +134,9 @@ namespace Discord.WebSocket
                 _tags = MessageHelper.ParseTags(text, Channel, guild, _userMentions);
                 model.Content = text;
             }
+
+            if (model.ReferencedMessage.IsSpecified && model.ReferencedMessage.Value != null)
+                _referencedMessage = RestUserMessage.Create(Discord, Channel, Author, model.ReferencedMessage.Value);
         }
 
         /// <inheritdoc />

test/Discord.Net.Tests.Unit/MockedEntities/MockedDMChannel.cs

@@ -73,17 +73,17 @@ namespace Discord
             throw new NotImplementedException();
         }
 
-        public Task<IUserMessage> SendFileAsync(string filePath, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
+        public Task<IUserMessage> SendFileAsync(string filePath, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
         {
             throw new NotImplementedException();
         }
 
-        public Task<IUserMessage> SendFileAsync(Stream stream, string filename, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
+        public Task<IUserMessage> SendFileAsync(Stream stream, string filename, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
         {
             throw new NotImplementedException();
         }
 
-        public Task<IUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null)
+        public Task<IUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
         {
             throw new NotImplementedException();
         }

test/Discord.Net.Tests.Unit/MockedEntities/MockedGroupChannel.cs

@@ -81,17 +81,17 @@ namespace Discord
             throw new NotImplementedException();
         }
 
-        public Task<IUserMessage> SendFileAsync(string filePath, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
+        public Task<IUserMessage> SendFileAsync(string filePath, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
         {
             throw new NotImplementedException();
         }
 
-        public Task<IUserMessage> SendFileAsync(Stream stream, string filename, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
+        public Task<IUserMessage> SendFileAsync(Stream stream, string filename, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
         {
             throw new NotImplementedException();
         }
 
-        public Task<IUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null)
+        public Task<IUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
         {
             throw new NotImplementedException();
         }

test/Discord.Net.Tests.Unit/MockedEntities/MockedTextChannel.cs

@@ -167,17 +167,17 @@ namespace Discord
             throw new NotImplementedException();
         }
 
-        public Task<IUserMessage> SendFileAsync(string filePath, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
+        public Task<IUserMessage> SendFileAsync(string filePath, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
         {
             throw new NotImplementedException();
         }
 
-        public Task<IUserMessage> SendFileAsync(Stream stream, string filename, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null)
+        public Task<IUserMessage> SendFileAsync(Stream stream, string filename, string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, bool isSpoiler = false, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
         {
             throw new NotImplementedException();
         }
 
-        public Task<IUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null)
+        public Task<IUserMessage> SendMessageAsync(string text = null, bool isTTS = false, Embed embed = null, RequestOptions options = null, AllowedMentions allowedMentions = null, MessageReference messageReference = null)
         {
             throw new NotImplementedException();
         }