Added required parameter to GetService

src/Discord.Net.Commands/CommandExtensions.cs

@@ -2,7 +2,7 @@
 {
     public static class CommandExtensions
     {
-		public static CommandService Commands(this DiscordClient client)
-			=> client.GetService<CommandService>();
+		public static CommandService Commands(this DiscordClient client, bool required = true)
+			=> client.GetService<CommandService>(required);
     }
 }

src/Discord.Net.Commands/Permissions/Levels/PermissionLevelChecker.cs

@@ -1,6 +1,4 @@
-using System;
-
-namespace Discord.Commands.Permissions.Levels
+namespace Discord.Commands.Permissions.Levels
 {
 	public class PermissionLevelChecker : IPermissionChecker
 	{
@@ -12,10 +10,8 @@ namespace Discord.Commands.Permissions.Levels
 
 		internal PermissionLevelChecker(DiscordClient client, int minPermissions)
 		{
-			_service = client.GetService<PermissionLevelService>();
+			_service = client.GetService<PermissionLevelService>(true);
 			_minPermissions = minPermissions;
-            if (_service == null)
-				throw new InvalidOperationException($"{nameof(PermissionLevelService)} must be added to {nameof(DiscordClient)} before this function is called.");
         }
 
 		public bool CanRun(Command command, User user, Channel channel)

src/Discord.Net.Commands/Permissions/Userlist/BlacklistChecker.cs

@@ -1,6 +1,4 @@
-using System;
-
-namespace Discord.Commands.Permissions.Userlist
+namespace Discord.Commands.Permissions.Userlist
 {
     public class BlacklistChecker : IPermissionChecker
 	{
@@ -8,9 +6,7 @@ namespace Discord.Commands.Permissions.Userlist
 
 		internal BlacklistChecker(DiscordClient client)
 		{
-			_service = client.GetService<BlacklistService>();
-			if (_service == null)
-				throw new InvalidOperationException($"{nameof(BlacklistService)} must be added to {nameof(DiscordClient)} before this function is called.");
+			_service = client.GetService<BlacklistService>(true);
 		}
 
 		public bool CanRun(Command command, User user, Channel channel)

src/Discord.Net.Commands/Permissions/Userlist/WhitelistChecker.cs

@@ -1,6 +1,4 @@
-using System;
-
-namespace Discord.Commands.Permissions.Userlist
+namespace Discord.Commands.Permissions.Userlist
 {
     public class WhitelistChecker : IPermissionChecker
 	{
@@ -8,9 +6,7 @@ namespace Discord.Commands.Permissions.Userlist
 
 		internal WhitelistChecker(DiscordClient client)
 		{
-			_service = client.GetService<WhitelistService>();
-			if (_service == null)
-				throw new InvalidOperationException($"{nameof(WhitelistService)} must be added to {nameof(DiscordClient)} before this function is called.");
+			_service = client.GetService<WhitelistService>(true);
 		}
 
 		public bool CanRun(Command command, User user, Channel channel)

src/Discord.Net.Modules/ModuleExtensions.cs

@@ -2,7 +2,7 @@
 {
     public static class ModuleExtensions
     {
-		public static ModuleService Modules(this DiscordClient client)
-			=> client.GetService<ModuleService>();
+		public static ModuleService Modules(this DiscordClient client, bool required = true)
+			=> client.GetService<ModuleService>(required);
     }
 }

src/Discord.Net.Modules/ModuleManager.cs

@@ -109,9 +109,7 @@ namespace Discord.Modules
 
 		public void CreateCommands(string prefix, Action<CommandGroupBuilder> config)
 		{
-			var commandService = _client.Commands();
-			if (commandService == null)
-				throw new InvalidOperationException($"{nameof(CommandService)} must be added to DiscordClient before this property is accessed.");
+			var commandService = _client.Commands(true);
 			commandService.CreateGroup(prefix, x =>
 			{
 				x.Category(_name);

src/Discord.Net/DiscordClient.cs

@@ -280,15 +280,20 @@ namespace Discord
 			obj.Install(this);
 			return obj;
 		}
-		public T GetService<T>()
+		public T GetService<T>(bool required = true)
 			where T : class, IService
 		{
 			IService service;
+			T serviceT = null;
 			if (_services.TryGetValue(typeof(T), out service))
-				return service as T;
+				serviceT = service as T;
 			else
 				return null;
-		}
+
+			if (serviceT == null && required)
+				throw new InvalidOperationException($"This operation requires {nameof(T)} to be added to {nameof(DiscordClient)}.");
+			return serviceT;
+        }
 
 		protected override IEnumerable<Task> GetTasks()
 		{