This is a Discord Bot made with C# that accepts plugins as extensions for more commands and events. All basic commands are built in already in the PluginManager class library. This project is based on:

Plugins

Requirements:

Visual Studio
.NET 6 (downloaded with Visual Studio)

Plugin Types:

Commands
Events
Slash Commands

How to create a plugin

First of all, Create a new project (class library) in Visual Studio. Then import the PluginManager.dll as project to your project.

1. Commands

Commands are loaded when all plugins are loaded into memory. When an user executes the command, only then the Execute function is called. Commands are plugins that allow users to interact with them. Here is an example:

using Discord;
using Discord.Commands;

using PluginManager.Interfaces;

namespace LevelingSystem;

internal class LevelCommand : DBCommand
{
    public string Command => "level";

    public List<string> Aliases => new() { "lvl" };

    public string Description => "Display tour current level";

    public string Usage => "level";

    public bool requireAdmin => false;

    public async void ExecuteServer(SocketCommandContext context)
    {
        object[] user = await Variables.database.ReadDataArrayAsync($"SELECT * FROM Levels WHERE UserID='{context.Message.Author.Id}'");
        if (user is null)
        {
            await context.Channel.SendMessageAsync("You are now unranked !");
            return;
        }

        int level = (int)user[1];
        int exp = (int)user[2];

        var builder = new EmbedBuilder();
        var r = new Random();
        builder.WithColor(r.Next(256), r.Next(256), r.Next(256));
        builder.AddField("Current Level", level, true)
               .AddField("Current EXP", exp, true)
               .AddField("Required Exp", (level * 8 + 24).ToString(), true);
        builder.WithTimestamp(DateTimeOffset.Now);
        builder.WithAuthor(context.Message.Author.Mention);
        await context.Channel.SendMessageAsync(embed: builder.Build());
    }
}

Code description:

Command - The keyword that triggers the execution for the command. This is what players must type in order to execute your command
Aliases - The aliases that can be used instead of the full name to execute the command
Description - The description of your command. Can be anything you like
Usage - The usage of your command. This is what help [Command] command will display
requireAdmin - true if this command requres an user with Administrator permission in the server
ExecuteServer () - the function that is executed only when the command is invoked in a server channel. (optional)
- context - the command context
ExecuteDM () - the function that is executed only when the command is invoked in a private (DM) channel. (optional)
- context - the command context

From here on, start coding. When your plugin is done, build it as any DLL project then add it to the following path {bot_executable}/Data/Plugins/<optional subfolder>/[your dll name].dll Then, reload bot and execute command lp in bot's console. The plugin should be loaded into memory or an error is thrown if not. If an error is thrown, then there is something wrong in your command's code.

2. Events

Events are loaded when all plugins are loaded. At the moment when they are loaded, the Start function is called. Events are used if you want the bot to do something when something happens in server. The following example shows you how to catch when a user joins the server and send to that user a DM message with Welcome to server !.

using PluginManager.Others;
using PluginManager.Interfaces;

public class OnUserJoin : DBEvent
{
    public string name => "MyEvent";

    public string description => "This is a demo event";

    public async void Start(Discord.WebSocket.DiscordSocketClient client)
    {
        Console.WriteLine($"Hello World from {name}");
        
        client.UserJoined += async (user) => {
            await (await user.CreateDMChannelAsync()).SendMessageAsync("Welcome to server !");
        };
    }
}

Code description:

name - The name of your event. It will appear in console when it loads
description - The description of your event
Start() - The main body of your event. This is executed when the bot loads all plugins
- client - the discord bot client

3. Slash Commands

Slash commands are server based commands. They work the same way as normal commands, but they require the / prefix as they are integrated with the UI of Discord. Here is an example:

using Discord;
using Discord.WebSocket;

using PluginManager.Interfaces;

namespace SlashCommands
{
    public class Random : DBSlashCommand
    {
        public string Name => "random";

        public string Description => "Generates a random nunber between 2 values";

        public bool canUseDM => true;

        public List<SlashCommandOptionBuilder> Options => new List<SlashCommandOptionBuilder>()
        {
            new SlashCommandOptionBuilder() {Name = "min-value", Description = "Minimum value", IsRequired=true, Type = ApplicationCommandOptionType.Integer, MinValue = 0, MaxValue = int.MaxValue-1},
            new SlashCommandOptionBuilder() {Name="max-value", Description = "Maximum value", IsRequired=true, Type=ApplicationCommandOptionType.Integer,MinValue = 0, MaxValue = int.MaxValue-1}
        };

        public async void ExecuteServer(SocketSlashCommand command)
        {
            var rnd = new System.Random();
            var options = command.Data.Options.ToArray();
            if (options.Count() != 2)
            {
                await command.RespondAsync("Invalid parameters", ephemeral: true);
                return;
            }

            Int64 numberOne = (Int64)options[0].Value;
            Int64 numberTwo = (Int64)options[1].Value;

            await command.RespondAsync("Your generated number is " + rnd.Next((int)numberOne, (int)numberTwo), ephemeral: true);

        }
    }
}

Code description:

Name - the command name (execute with /{Name})
Description - The description of the command
canUseDM - true id this command can be activated in DM chat, false otherwise
Options - the arguments of the command
ExecuteServer() - this function will be called if the command is invoked in a server channel (optional)
- context - the command context
ExecuteDM() - this function will be called if the command is invoked in a DM channel (optional)
- context - the command context