Custom Argument Converter

Writing your own argument converter will enable you to convert custom types and replace the functionality of existing converters. Like many things in DSharpPlus, doing this is straightforward and simple.

First, create a new class which implements IArgumentConverter<T> and its method ConvertAsync(string, CommandContext). Our example will be a boolean converter, so we'll also pass bool as the type parameter for IArgumentConverter<T>.

public class CustomArgumentConverter : IArgumentConverter<bool>
{
    public Task<Optional<bool>> ConvertAsync(string value, CommandContext ctx)
    {
        if (bool.TryParse(value, out var boolean))
        {
            return Task.FromResult(Optional.FromValue(boolean));
        }           

        switch (value.ToLower())
        {
            case "yes":
            case "y":
            case "t":
                return Task.FromResult(Optional.FromValue(true));

            case "no":
            case "n":
            case "f":
                return Task.FromResult(Optional.FromValue(false));

            default:
                return Task.FromResult(Optional.FromNoValue<bool>());
        } 
    } 
}

Then register the argument converter with CommandContext.

var discord = new DiscordClient();
var commands = discord.UseCommandsNext();

commands.RegisterConverter(new CustomArgumentConverter());

Once the argument converter is written and registered, we'll be able to use it:

[Command("boolean")]
public async Task BooleanCommand(CommandContext ctx, bool boolean)
{
    await ctx.RespondAsync($"Converted to {boolean}");
}