70 lines
3.1 KiB
Markdown
70 lines
3.1 KiB
Markdown
|
---
|
||
|
|
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:
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
### 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](xref:Guides.DI.Injection) for further information.
|