Introduction

.NET Generic Host
Bare Bones

Adding application commands with the .NET Generic Host is very easy. Use AddApplicationCommands(IServiceCollection) to add the application command service to your host builder. Then, use AddSlashCommand, AddUserCommand or AddMessageCommand to add an application command using the minimal APIs way and/or use AddModules(IHost, Assembly) to add application command modules from an assembly. You also need to use UseGatewayEventHandlers(IHost) to bind the service event handlers.

using Microsoft.Extensions.Hosting;

using NetCord;
using NetCord.Hosting.Gateway;
using NetCord.Hosting.Services;
using NetCord.Hosting.Services.ApplicationCommands;
using NetCord.Rest;

var builder = Host.CreateApplicationBuilder(args);

builder.Services
    .AddDiscordGateway()
    .AddApplicationCommands();

var host = builder.Build();

// Add commands using minimal APIs
host.AddSlashCommand("ping", "Ping!", () => "Pong!")
    .AddUserCommand("Username", (User user) => user.Username)
    .AddMessageCommand("Length", (RestMessage message) => message.Content.Length.ToString());

// Add commands from modules
host.AddModules(typeof(Program).Assembly);

// Add handlers to handle the commands
host.UseGatewayEventHandlers();

await host.RunAsync();

First, add the following lines to the using section.

using NetCord.Rest;
using NetCord.Services;
using NetCord.Services.ApplicationCommands;

Now, it's time to create ApplicationCommandService<TContext> instance and add application commands to it. You can do it by using AddSlashCommand, AddUserCommand or AddMessageCommand to add an application command using the minimal APIs way and/or by using AddModules(Assembly) to add application command modules from an assembly.

// Create the application command service
ApplicationCommandService<ApplicationCommandContext> applicationCommandService = new();

// Add commands using minimal APIs
applicationCommandService.AddSlashCommand("ping", "Ping!", () => "Pong!");
applicationCommandService.AddUserCommand("Username", (User user) => user.Username);
applicationCommandService.AddMessageCommand("Length", (RestMessage message) => message.Content.Length.ToString());

// Add commands from modules
applicationCommandService.AddModules(typeof(Program).Assembly);

We can add a command handler now. If you used a context other than ApplicationCommandContext, you may need to change the interaction type of the handler to the appropriate one.

// Add the handler to handle interactions
client.InteractionCreate += async interaction =>
{
    // Check if the interaction is an application command interaction
    if (interaction is not ApplicationCommandInteraction applicationCommandInteraction)
        return;

    // Execute the command
    var result = await applicationCommandService.ExecuteAsync(new ApplicationCommandContext(applicationCommandInteraction, client));

    // Check if the execution failed
    if (result is not IFailResult failResult)
        return;

    // Return the error message to the user if the execution failed
    try
    {
        await interaction.SendResponseAsync(InteractionCallback.Message(failResult.Message));
    }
    catch
    {
    }
};

Now, we should send the commands to Discord, to make them usable. Add the following line under the handler:

// Create the commands so that you can use them in the Discord client
await applicationCommandService.CreateCommandsAsync(client.Rest, client.Id);

The Final Product

Program.cs

using NetCord;
using NetCord.Gateway;
using NetCord.Rest;
using NetCord.Services;
using NetCord.Services.ApplicationCommands;

GatewayClient client = new(new BotToken("Token from Discord Developer Portal"), new GatewayClientConfiguration()
{
    Intents = default,
});

// Create the application command service
ApplicationCommandService<ApplicationCommandContext> applicationCommandService = new();

// Add commands using minimal APIs
applicationCommandService.AddSlashCommand("ping", "Ping!", () => "Pong!");
applicationCommandService.AddUserCommand("Username", (User user) => user.Username);
applicationCommandService.AddMessageCommand("Length", (RestMessage message) => message.Content.Length.ToString());

// Add commands from modules
applicationCommandService.AddModules(typeof(Program).Assembly);

// Add the handler to handle interactions
client.InteractionCreate += async interaction =>
{
    // Check if the interaction is an application command interaction
    if (interaction is not ApplicationCommandInteraction applicationCommandInteraction)
        return;

    // Execute the command
    var result = await applicationCommandService.ExecuteAsync(new ApplicationCommandContext(applicationCommandInteraction, client));

    // Check if the execution failed
    if (result is not IFailResult failResult)
        return;

    // Return the error message to the user if the execution failed
    try
    {
        await interaction.SendResponseAsync(InteractionCallback.Message(failResult.Message));
    }
    catch
    {
    }
};

// Create the commands so that you can use them in the Discord client
await applicationCommandService.CreateCommandsAsync(client.Rest, client.Id);

client.Log += message =>
{
    Console.WriteLine(message);
    return default;
};

await client.StartAsync();
await Task.Delay(-1);

Note

If you don't see the commands in Discord, try refreshing the Discord client using Ctrl + R on PC or ⌘ + R on Mac.

Important

Please note that names of slash commands must be lowercase.

Example Module

Here you can see an example module showing how to use modules with application commands.

using NetCord;
using NetCord.Rest;
using NetCord.Services.ApplicationCommands;

namespace MyBot;

public class ExampleModule : ApplicationCommandModule<ApplicationCommandContext>
{
    [SlashCommand("pong", "Pong!")]
    public static string Pong() => "Ping!";

    [UserCommand("ID")]
    public static string Id(User user) => user.Id.ToString();

    [MessageCommand("Timestamp")]
    public static string Timestamp(RestMessage message) => message.CreatedAt.ToString();
}

Table of Contents

Introduction

Note

Important

Example Module