.NET8依賴註入新特性Keyed services

什麼是Keyed service

Keyed service是指，為一個需要註入的服務定義一個Key Name，並使用使用Key Name檢索依賴項註入 (DI) 服務的機制。

使用方法

通過調用 AddKeyedSingleton （或 AddKeyedScoped 或 AddKeyedTransient）來註冊服務，與Key Name相關聯。或使用 [FromKeyedServices] 屬性指定密鑰來訪問已註冊的服務。

以下代碼演示如何使用Keyed service:

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.SignalR;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddKeyedSingleton<ICache, BigCache>("big");
builder.Services.AddKeyedSingleton<ICache, SmallCache>("small");
builder.Services.AddControllers();

var app = builder.Build();

app.MapGet("/big", ([FromKeyedServices("big")] ICache bigCache) => bigCache.Get("date"));
app.MapGet("/small", ([FromKeyedServices("small")] ICache smallCache) =>
                                                               smallCache.Get("date"));

app.MapControllers();

app.Run();

public interface ICache
{
    object Get(string key);
}
public class BigCache : ICache
{
    public object Get(string key) => $"Resolving {key} from big cache.";
}

public class SmallCache : ICache
{
    public object Get(string key) => $"Resolving {key} from small cache.";
}

[ApiController]
[Route("/cache")]
public class CustomServicesApiController : Controller
{
    [HttpGet("big-cache")]
    public ActionResult<object> GetOk([FromKeyedServices("big")] ICache cache)
    {
        return cache.Get("data-mvc");
    }
}

public class MyHub : Hub
{
    public void Method([FromKeyedServices("small")] ICache cache)
    {
        Console.WriteLine(cache.Get("signalr"));
    }
}

Blazor中的支持

[Inject(Key = "my-service")]
public IMyService MyService { get; set; }