docs: Improved DI documentation (#2407)

docs/guides/dependency_injection/basics.md

@@ -0,0 +1,69 @@
+---
+uid: Guides.DI.Intro
+title: Introduction
+---
+
+# Dependency Injection
+
+Dependency injection is a feature not required in Discord.Net, but makes it a lot easier to use.
+It can be combined with a large number of other libraries, and gives you better control over your application.
+
+> Further into the documentation, Dependency Injection will be referred to as 'DI'.
+
+## Installation
+
+DI is not native to .NET. You need to install the extension packages to your project in order to use it:
+
+- [Meta](https://www.nuget.org/packages/Microsoft.Extensions.DependencyInjection/).
+- [Abstractions](https://www.nuget.org/packages/Microsoft.Extensions.DependencyInjection.Abstractions/).
+
+> [!WARNING]
+> Downloading the abstractions package alone will not give you access to required classes to use DI properly.
+> Please install both packages, or choose to only install the meta package to implicitly install both.
+
+### Visual Package Manager:
+
+[Installing](images/manager.png)
+
+### Command Line:
+
+`PM> Install-Package Microsoft.Extensions.DependencyInjection`.
+
+> [!TIP]
+> ASP.NET already comes packed with all the necessary assemblies in its framework.
+> You do not require to install any additional NuGet packages to make full use of all features of DI in ASP.NET projects.
+
+## Getting started
+
+First of all, you will need to create an application based around dependency injection,
+which in order will be able to access and inject them across the project.
+
+[!code-csharp[Building the Program](samples/program.cs)]
+
+In order to freely pass around your dependencies in different classes,
+you will need to register them to a new `ServiceCollection` and build them into an `IServiceProvider` as seen above.
+The IServiceProvider then needs to be accessible by the startup file, so you can access your provider and manage them.
+
+[!code-csharp[Building the Collection](samples/collection.cs)]
+
+As shown above, an instance of `DiscordSocketConfig` is created, and added **before** the client itself is.
+Because the collection will prefer to create the highest populated constructor available with the services already present,
+it will prefer the constructor with the configuration, because you already added it.
+
+## Using your dependencies
+
+After building your provider in the Program class constructor, the provider is now available inside the instance you're actively using.
+Through the provider, we can ask for the DiscordSocketClient we registered earlier.
+
+[!code-csharp[Applying DI in RunAsync](samples/runasync.cs)]
+
+> [!WARNING]
+> Service constructors are not activated until the service is **first requested**.
+> An 'endpoint' service will have to be requested from the provider before it is activated.
+> If a service is requested with dependencies, its dependencies (if not already active) will be activated before the service itself is.
+
+## Injecting dependencies
+
+You can not only directly access the provider from a field or property, but you can also pass around instances to classes registered in the provider.
+There are multiple ways to do this. Please refer to the
+[Injection Documentation](Guides.DI.Injection) for further information.

docs/guides/dependency_injection/injection.md

@@ -0,0 +1,44 @@
+---
+uid: Guides.DI.Injection
+title: Injection
+---
+
+# Injecting instances within the provider
+
+You can inject registered services into any class that is registered to the `IServiceProvider`.
+This can be done through property or constructor.
+
+> [!NOTE]
+> As mentioned above, the dependency *and* the target class have to be registered in order for the serviceprovider to resolve it.
+
+## Injecting through a constructor
+
+Services can be injected from the constructor of the class.
+This is the preferred approach, because it automatically locks the readonly field in place with the provided service and isn't accessible outside of the class.
+
+[!code-csharp[Property Injection(samples/property-injecting.cs)]]
+
+## Injecting through properties
+
+Injecting through properties is also allowed as follows.
+
+[!code-csharp[Property Injection](samples/property-injecting.cs)]
+
+> [!WARNING]
+> Dependency Injection will not resolve missing services in property injection, and it will not pick a constructor instead.
+> If a publically accessible property is attempted to be injected and its service is missing, the application will throw an error.
+
+## Using the provider itself
+
+You can also access the provider reference itself from injecting it into a class. There are multiple use cases for this:
+
+- Allowing libraries (Like Discord.Net) to access your provider internally.
+- Injecting optional dependencies.
+- Calling methods on the provider itself if necessary, this is often done for creating scopes.
+
+[!code-csharp[Provider Injection](samples/provider.cs)]
+
+> [!NOTE]
+> It is important to keep in mind that the provider will pick the 'biggest' available constructor.
+> If you choose to introduce multiple constructors,
+> keep in mind that services missing from one constructor may have the provider pick another one that *is* available instead of throwing an exception.

docs/guides/dependency_injection/samples/access-activator.cs

@@ -0,0 +1,9 @@
+async Task RunAsync()
+{
+    //...
+
+    await _serviceProvider.GetRequiredService<ServiceActivator>()
+        .ActivateAsync();
+
+    //...
+}

docs/guides/dependency_injection/samples/collection.cs

@@ -0,0 +1,13 @@
+static IServiceProvider CreateServices()
+{
+    var config = new DiscordSocketConfig()
+    {
+        //...
+    };
+
+    var collection = new ServiceCollection()
+        .AddSingleton(config)
+        .AddSingleton<DiscordSocketClient>();
+
+    return collection.BuildServiceProvider();
+}

docs/guides/dependency_injection/samples/ctor-injecting.cs

@@ -0,0 +1,14 @@
+public class ClientHandler
+{
+    private readonly DiscordSocketClient _client;
+
+    public ClientHandler(DiscordSocketClient client)
+    {
+        _client = client;
+    }
+
+    public async Task ConfigureAsync()
+    {
+        //...
+    }
+}

docs/guides/dependency_injection/samples/enumeration.cs

@@ -0,0 +1,18 @@
+public class ServiceActivator
+{
+    // This contains *all* registered services of serviceType IService
+    private readonly IEnumerable<IService> _services;
+
+    public ServiceActivator(IEnumerable<IService> services)
+    {
+        _services = services;
+    }
+
+    public async Task ActivateAsync()
+    {
+        foreach(var service in _services)
+        {
+            await service.StartAsync();
+        }
+    }
+}

docs/guides/dependency_injection/samples/implicit-registration.cs

@@ -0,0 +1,12 @@
+public static ServiceCollection RegisterImplicitServices(this ServiceCollection collection, Type interfaceType, Type activatorType)
+{
+    // Get all types in the executing assembly. There are many ways to do this, but this is fastest.
+    foreach (var type in typeof(Program).Assembly.GetTypes())
+    {
+        if (interfaceType.IsAssignableFrom(type) && !type.IsAbstract)
+            collection.AddSingleton(interfaceType, type);
+    }
+
+    // Register the activator so you can activate the instances.
+    collection.AddSingleton(activatorType);
+}

docs/guides/dependency_injection/samples/modules.cs

@@ -0,0 +1,16 @@
+public class MyModule : InteractionModuleBase
+{
+    private readonly MyService _service;
+
+    public MyModule(MyService service)
+    {
+        _service = service;
+    }
+
+    [SlashCommand("things", "Shows things")]
+    public async Task ThingsAsync()
+    {
+        var str = string.Join("\n", _service.Things)
+        await RespondAsync(str);
+    }
+}

docs/guides/dependency_injection/samples/program.cs

@@ -0,0 +1,24 @@
+public class Program
+{
+    private readonly IServiceProvider _serviceProvider;
+
+    public Program()
+    {
+        _serviceProvider = CreateProvider();
+    }
+
+    static void Main(string[] args)
+        => new Program().RunAsync(args).GetAwaiter().GetResult();
+
+    static IServiceProvider CreateProvider()
+    {
+        var collection = new ServiceCollection();
+        //...
+        return collection.BuildServiceProvider();
+    }
+
+    async Task RunAsync(string[] args)
+    {
+        //...
+    }
+}

docs/guides/dependency_injection/samples/property-injecting.cs

@@ -0,0 +1,9 @@
+public class ClientHandler
+{
+    public DiscordSocketClient Client { get; set; }
+
+    public async Task ConfigureAsync()
+    {
+        //...
+    }
+}

docs/guides/dependency_injection/samples/provider.cs

@@ -0,0 +1,26 @@
+public class UtilizingProvider
+{
+    private readonly IServiceProvider _provider;
+    private readonly AnyService _service;
+
+    // This service is allowed to be null because it is only populated if the service is actually available in the provider.
+    private readonly AnyOtherService? _otherService;
+
+    // This constructor injects only the service provider,
+    // and uses it to populate the other dependencies.
+    public UtilizingProvider(IServiceProvider provider)
+    {
+        _provider = provider;
+        _service = provider.GetRequiredService<AnyService>();
+        _otherService = provider.GetService<AnyOtherService>();
+    }
+
+    // This constructor injects the service provider, and AnyService,
+    // making sure that AnyService is not null without having to call GetRequiredService
+    public UtilizingProvider(IServiceProvider provider, AnyService service)
+    {
+        _provider = provider;
+        _service = service;
+        _otherService = provider.GetService<AnyOtherService>();
+    }
+}

docs/guides/dependency_injection/samples/runasync.cs

@@ -0,0 +1,17 @@
+async Task RunAsync(string[] args)
+{
+    // Request the instance from the client.
+    // Because we're requesting it here first, its targetted constructor will be called and we will receive an active instance.
+    var client = _services.GetRequiredService<DiscordSocketClient>();
+
+    client.Log += async (msg) =>
+    {
+        await Task.CompletedTask;
+        Console.WriteLine(msg);
+    }
+
+    await client.LoginAsync(TokenType.Bot, "");
+    await client.StartAsync();
+
+    await Task.Delay(Timeout.Infinite);
+}

docs/guides/dependency_injection/samples/scoped.cs

@@ -0,0 +1,6 @@
+
+// With serviceType:
+collection.AddScoped<IScopedService, ScopedService>();
+
+// Without serviceType:
+collection.AddScoped<ScopedService>();

docs/guides/dependency_injection/samples/service-registration.cs

@@ -0,0 +1,21 @@
+static IServiceProvider CreateServices()
+{
+    var config = new DiscordSocketConfig()
+    {
+        //...
+    };
+
+    // X represents either Interaction or Command, as it functions the exact same for both types.
+    var servConfig = new XServiceConfig()
+    {
+        //...
+    }
+
+    var collection = new ServiceCollection()
+        .AddSingleton(config)
+        .AddSingleton<DiscordSocketClient>()
+        .AddSingleton(servConfig)
+        .AddSingleton<XService>();
+
+    return collection.BuildServiceProvider();
+}

docs/guides/dependency_injection/samples/services.cs

@@ -0,0 +1,9 @@
+public class MyService
+{
+    public List<string> Things { get; }
+
+    public MyService()
+    {
+        Things = new();
+    }
+}

docs/guides/dependency_injection/samples/singleton.cs

@@ -0,0 +1,6 @@
+
+// With serviceType:
+collection.AddSingleton<ISingletonService, SingletonService>();
+
+// Without serviceType:
+collection.AddSingleton<SingletonService>();

docs/guides/dependency_injection/samples/transient.cs

@@ -0,0 +1,6 @@
+
+// With serviceType:
+collection.AddTransient<ITransientService, TransientService>();
+
+// Without serviceType:
+collection.AddTransient<TransientService>();

docs/guides/dependency_injection/scaling.md

@@ -0,0 +1,39 @@
+---
+uid: Guides.DI.Scaling
+title: Scaling your DI
+---
+
+# Scaling your DI 
+
+Dependency injection has a lot of use cases, and is very suitable for scaled applications.
+There are a few ways to make registering & using services easier in large amounts.
+
+## Using a range of services.
+
+If you have a lot of services that all have the same use such as handling an event or serving a module,
+you can register and inject them all at once by some requirements:
+
+- All classes need to inherit a single interface or abstract type.
+- While not required, it is preferred if the interface and types share a method to call on request.
+- You need to register a class that all the types can be injected into.
+
+### Registering implicitly
+
+Registering all the types is done through getting all types in the assembly and checking if they inherit the target interface.
+
+[!code-csharp[Registering](samples/implicit-registration.cs)]
+
+> [!NOTE]
+> As seen above, the interfaceType and activatorType are undefined. For our usecase below, these are `IService` and `ServiceActivator` in order.
+
+### Using implicit dependencies
+
+In order to use the implicit dependencies, you have to get access to the activator you registered earlier.
+
+[!code-csharp[Accessing the activator](samples/access-activator.cs)]
+
+When the activator is accessed and the `ActivateAsync()` method is called, the following code will be executed:
+
+[!code-csharp[Executing the activator](samples/enumeration.cs)]
+
+As a result of this, all the services that were registered with `IService` as its implementation type will execute their starting code, and start up.

docs/guides/dependency_injection/services.md

@@ -0,0 +1,48 @@
+---
+uid: Guides.DI.Services
+title: Using DI in Interaction & Command Frameworks
+---
+
+# DI in the Interaction- & Command Service
+
+For both the Interaction- and Command Service modules, DI is quite straight-forward to use.
+
+You can inject any service into modules without the modules having to be registered to the provider.
+Discord.Net resolves your dependencies internally.
+
+> [!WARNING]
+> The way DI is used in the Interaction- & Command Service are nearly identical, except for one detail:
+> [Resolving Module Dependencies](xref:Guides.IntFw.Intro#resolving-module-dependencies)
+
+## Registering the Service
+
+Thanks to earlier described behavior of allowing already registered members as parameters of the available ctors,
+The socket client & configuration will automatically be acknowledged and the XService(client, config) overload will be used.
+
+[!code-csharp[Service Registration](samples/service-registration.cs)]
+
+## Usage in modules
+
+In the constructor of your module, any parameters will be filled in by
+the @System.IServiceProvider that you've passed.
+
+Any publicly settable properties will also be filled in the same
+manner.
+
+[!code-csharp[Module Injection](samples/modules.cs)]
+
+If you accept `Command/InteractionService` or `IServiceProvider` as a parameter in your constructor or as an injectable property,
+these entries will be filled by the `Command/InteractionService` that the module is loaded from and the `IServiceProvider` that is passed into it respectively.
+
+> [!NOTE]
+> Annotating a property with a [DontInjectAttribute] attribute will
+> prevent the property from being injected.
+
+## Services
+
+Because modules are transient of nature and will reinstantiate on every request,
+it is suggested to create a singleton service behind it to hold values across multiple command executions.
+
+[!code-csharp[Services](samples/services.cs)]
+
+

docs/guides/dependency_injection/types.md

@@ -0,0 +1,52 @@
+---
+uid: Guides.DI.Dependencies
+title: Types of Dependencies
+---
+
+# Dependency Types
+
+There are 3 types of dependencies to learn to use. Several different usecases apply for each.
+
+> [!WARNING]
+> When registering types with a serviceType & implementationType,
+> only the serviceType will be available for injection, and the implementationType will be used for the underlying instance.
+
+## Singleton
+
+A singleton service creates a single instance when first requested, and maintains that instance across the lifetime of the application.
+Any values that are changed within a singleton will be changed across all instances that depend on it, as they all have the same reference to it.
+
+### Registration:
+
+[!code-csharp[Singleton Example](samples/singleton.cs)]
+
+> [!NOTE]
+> Types like the Discord client and Interaction/Command services are intended to be singleton,
+> as they should last across the entire app and share their state with all references to the object.
+
+## Scoped
+
+A scoped service creates a new instance every time a new service is requested, but is kept across the 'scope'.
+As long as the service is in view for the created scope, the same instance is used for all references to the type.
+This means that you can reuse the same instance during execution, and keep the services' state for as long as the request is active.
+
+### Registration:
+
+[!code-csharp[Scoped Example](samples/scoped.cs)]
+
+> [!NOTE]
+> Without using HTTP or libraries like EFCORE, scopes are often unused in Discord bots.
+> They are most commonly used for handling HTTP and database requests.
+
+## Transient
+
+A transient service is created every time it is requested, and does not share its state between references within the target service.
+It is intended for lightweight types that require little state, to be disposed quickly after execution.
+
+### Registration:
+
+[!code-csharp[Transient Example](samples/transient.cs)]
+
+> [!NOTE]
+> Discord.Net modules behave exactly as transient types, and are intended to only last as long as the command execution takes.
+> This is why it is suggested for apps to use singleton services to keep track of cross-execution data.

docs/guides/int_framework/dependency-injection.md

@@ -1,13 +0,0 @@
----
-uid: Guides.IntFw.DI
-title: Dependency Injection
----
-
-# Dependency Injection
-
-Dependency injection in the Interaction Service is mostly based on that of the Text-based command service,
-for which further information is found [here](xref:Guides.TextCommands.DI).
-
-> [!NOTE]
-> The 2 are nearly identical, except for one detail:
-> [Resolving Module Dependencies](xref:Guides.IntFw.Intro#resolving-module-dependencies)

docs/guides/int_framework/intro.md

@@ -374,8 +374,7 @@ delegate can be used to create HTTP responses from a deserialized json object st
 - Use the interaction endpoints of the module base instead of the interaction object (ie. `RespondAsync()`, `FollowupAsync()`...).
 
 [AutocompleteHandlers]: xref:Guides.IntFw.AutoCompletion
-[DependencyInjection]: xref:Guides.TextCommands.DI
-[Post Execution Docuemntation]: xref:Guides.IntFw.PostExecution
+[DependencyInjection]: xref:Guides.DI.Intro
 
 [GroupAttribute]: xref:Discord.Interactions.GroupAttribute
 [InteractionService]: xref:Discord.Interactions.InteractionService

docs/guides/text_commands/dependency-injection.md

@@ -1,51 +0,0 @@
----
-uid: Guides.TextCommands.DI
-title: Dependency Injection
----
-
-# Dependency Injection
-
-The Text Command Service is bundled with a very barebone Dependency
-Injection service for your convenience. It is recommended that you use
-DI when writing your modules.
-
-> [!WARNING]
-> If you were brought here from the Interaction Service guides,
-> make sure to replace all namespaces that imply `Discord.Commands` with `Discord.Interactions`
-
-## Setup
-
-1. Create a @Microsoft.Extensions.DependencyInjection.ServiceCollection.
-2. Add the dependencies to the service collection that you wish
- to use in the modules.
-3. Build the service collection into a service provider.
-4. Pass the service collection into @Discord.Commands.CommandService.AddModulesAsync* / @Discord.Commands.CommandService.AddModuleAsync* , @Discord.Commands.CommandService.ExecuteAsync* .
-
-### Example - Setting up Injection
-
-[!code-csharp[IServiceProvider Setup](samples/dependency-injection/dependency_map_setup.cs)]
-
-## Usage in Modules
-
-In the constructor of your module, any parameters will be filled in by
-the @System.IServiceProvider that you've passed.
-
-Any publicly settable properties will also be filled in the same
-manner.
-
-> [!NOTE]
-> Annotating a property with a [DontInjectAttribute] attribute will
-> prevent the property from being injected.
-
-> [!NOTE]
-> If you accept `CommandService` or `IServiceProvider` as a parameter
-> in your constructor or as an injectable property, these entries will
-> be filled by the `CommandService` that the module is loaded from and
-> the `IServiceProvider` that is passed into it respectively.
-
-### Example - Injection in Modules
-
-[!code-csharp[Injection Modules](samples/dependency-injection/dependency_module.cs)]
-[!code-csharp[Disallow Dependency Injection](samples/dependency-injection/dependency_module_noinject.cs)]
-
-[DontInjectAttribute]: xref:Discord.Commands.DontInjectAttribute

docs/guides/text_commands/intro.md

@@ -187,7 +187,7 @@ service provider.
 
 ### Module Constructors
 
-Modules are constructed using [Dependency Injection](xref:Guides.TextCommands.DI). Any parameters
+Modules are constructed using [Dependency Injection](xref:Guides.DI.Intro). Any parameters
 that are placed in the Module's constructor must be injected into an
 @System.IServiceProvider first.
 

docs/guides/text_commands/samples/dependency-injection/dependency_map_setup.cs

@@ -1,65 +0,0 @@
-public class Initialize
-{
-	private readonly CommandService _commands;
-	private readonly DiscordSocketClient _client;
-
-	// Ask if there are existing CommandService and DiscordSocketClient
-	// instance. If there are, we retrieve them and add them to the
-	// DI container; if not, we create our own.
-	public Initialize(CommandService commands = null, DiscordSocketClient client = null)
-	{
-		_commands = commands ?? new CommandService();
-		_client = client ?? new DiscordSocketClient();
-	}
-
-	public IServiceProvider BuildServiceProvider() => new ServiceCollection()
-		.AddSingleton(_client)
-		.AddSingleton(_commands)
-		// You can pass in an instance of the desired type
-		.AddSingleton(new NotificationService())
-		// ...or by using the generic method.
-		//
-		// The benefit of using the generic method is that 
-		// ASP.NET DI will attempt to inject the required
-		// dependencies that are specified under the constructor 
-		// for us.
-		.AddSingleton<DatabaseService>()
-		.AddSingleton<CommandHandler>()
-		.BuildServiceProvider();
-}
-public class CommandHandler
-{
-	private readonly DiscordSocketClient _client;
-	private readonly CommandService _commands;
-	private readonly IServiceProvider _services;
-
-	public CommandHandler(IServiceProvider services, CommandService commands, DiscordSocketClient client)
-	{
-		_commands = commands;
-		_services = services;
-		_client = client;
-	}
-
-	public async Task InitializeAsync()
-	{
-		// Pass the service provider to the second parameter of
-		// AddModulesAsync to inject dependencies to all modules 
-		// that may require them.
-		await _commands.AddModulesAsync(
-			assembly: Assembly.GetEntryAssembly(), 
-			services: _services);
-		_client.MessageReceived += HandleCommandAsync;
-	}
-
-	public async Task HandleCommandAsync(SocketMessage msg)
-	{
-		// ...
-		// Pass the service provider to the ExecuteAsync method for
-		// precondition checks.
-		await _commands.ExecuteAsync(
-			context: context, 
-			argPos: argPos, 
-			services: _services);
-		// ...
-	}
-}

docs/guides/text_commands/samples/dependency-injection/dependency_module.cs

@@ -1,37 +0,0 @@
-// After setting up dependency injection, modules will need to request
-// the dependencies to let the library know to pass 
-// them along during execution.
-
-// Dependency can be injected in two ways with Discord.Net.
-// You may inject any required dependencies via...
-// the module constructor
-// -or-
-// public settable properties
-
-// Injection via constructor
-public class DatabaseModule : ModuleBase<SocketCommandContext>
-{
-    private readonly DatabaseService _database;
-    public DatabaseModule(DatabaseService database)
-    {
-        _database = database;
-    }
-
-    [Command("read")]
-    public async Task ReadFromDbAsync()
-    {
-        await ReplyAsync(_database.GetData());
-    }
-}
-
-// Injection via public settable properties
-public class DatabaseModule : ModuleBase<SocketCommandContext>
-{
-    public DatabaseService DbService { get; set; }
-
-    [Command("read")]
-    public async Task ReadFromDbAsync()
-    {
-        await ReplyAsync(DbService.GetData());
-    }
-}

docs/guides/text_commands/samples/dependency-injection/dependency_module_noinject.cs

@@ -1,29 +0,0 @@
-// Sometimes injecting dependencies automatically with the provided
-// methods in the prior example may not be desired.
-
-// You may explicitly tell Discord.Net to **not** inject the properties
-// by either...
-// restricting the access modifier
-// -or-
-// applying DontInjectAttribute to the property
-
-// Restricting the access modifier of the property
-public class ImageModule : ModuleBase<SocketCommandContext>
-{
-    public ImageService ImageService { get; }
-    public ImageModule()
-    {
-        ImageService = new ImageService();
-    }
-}
-
-// Applying DontInjectAttribute
-public class ImageModule : ModuleBase<SocketCommandContext>
-{
-    [DontInject]
-    public ImageService ImageService { get; set; }
-    public ImageModule()
-    {
-        ImageService = new ImageService();
-    }
-}