Add doc page for Named Arguments

docs/guides/commands/namedarguments.md

@@ -0,0 +1,75 @@
+---
+uid: Guides.Commands.NamedArguments
+title: Named Arguments
+---
+
+# Named Arguments
+
+By default, arguments for commands are parsed positionally, meaning
+that the order matters. But sometimes you may want to define a command
+with many optional parameters and it'd be easier for users to specify
+only what they want to set instead of needing them to specify everything.
+
+## Setting up Named Arguments
+
+In order to be able to specify different arguments by name, you have
+to create a new class that contains all of the optional values that
+the command will use and applying an instance of
+[`NamedArgumentTypeAttribute`](xref:Discord.Commands.NamedArgumentTypeAttribute) on it.
+
+### Example - Creating a Named Arguments Type
+
+```cs
+[NamedArgumentType]
+public class NamableArguments
+{
+    public string First { get; set; }
+    public string Second { get; set; }
+    public string Third { get; set; }
+    public string Fourth { get; set; }
+}
+```
+
+## Use in a command
+
+The command where you want to use these values can be declared like so:
+```cs
+[Command("act")]
+public async Task Act(int requiredArg, NamableArguments namedArgs)
+```
+
+A TypeReader for the named arguments container type is
+automatically registered.
+It's important that any other arguments that would be required
+are placed before the container type.
+
+> [!IMPORTANT]
+> A single command can have only __one__ parameter of a
+> type annotated with `[NamedArgumentType]` and it
+> **MUST** be the last parameter in the list.
+> A command parameter of such an annotated type
+> is automatically treated as if that parameter
+> has [`[Remainder]`](xref:Discord.Commands.RemainderAttribute)
+
+The command can now be invoked as follows:
+`.act 42 first: Hello fourth: "A string with spaces must be wrapped in quotes" second: World`
+
+## Complex types
+
+The TypeReader for Named Argument Types will look for a TypeReader
+of every property type, meaning any other command parameter type
+will work just the same.
+
+You can also read multiple values into a single property
+by making that property an `IEnumerable<T>`. So if your
+Named Argument Type has, for example:
+```cs
+public IEnumerable<int> Numbers { get; set; }
+```
+the command can be invoked as:
+`.cmd numbers: "1, 2, 4, 8, 16, 32"`
+
+## Additional
+
+The use of [`[OverrideTypeReader]`](xref:Discord.Commands.OverrideTypeReaderAttribute)
+is also supported on the properties of a Named Argument Type.

docs/guides/toc.yml

@@ -27,6 +27,8 @@
       topicUid: Guides.Commands.Intro
     - name: TypeReaders
       topicUid: Guides.Commands.TypeReaders
+    - name: Named Arguments
+      topicUid: Guides.Commands.NamedArguments
     - name: Preconditions
       topicUid: Guides.Commands.Preconditions
     - name: Dependency Injection