什么是Keyed service
Keyed service是指，为一个需要注入的服务定义一个Key Name，并使用使用Key Name检索依赖项注入 (DI) 服务的机制。
使用方法
通过调用 AddKeyedSingleton （或 AddKeyedScoped 或 AddKeyedTransient）来注册服务，与Key Name相关联。或使用 [FromKeyedServices] 属性指定密钥来访问已注册的服务。
以下代码演示如何使用Keyed service:
代码语言：javascript复制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
Blazor 现在支持使用 [Inject] 属性注入Keyed Service。Keyed Service在使用依赖项注入时界定服务的注册和使用范围。 使用新 InjectAttribute.Key 属性指定服务要注入的Service：
代码语言：javascript复制[Inject(Key = "my-service")]
public IMyService MyService { get; set; }@inject Razor 指令尚不支持Keyed Service，但将来的版本会对此进行改进。 参考地址 https://learn.microsoft.com/zh-cn/aspnet/core/release-notes/aspnetcore-8.0?view=aspnetcore-8.0#keyed-services-support-in-dependency-injection https://learn.microsoft.com/zh-cn/aspnet/core/fundamentals/dependency-injection?view=aspnetcore-8.0#keyed-services https://learn.microsoft.com/zh-cn/aspnet/core/release-notes/aspnetcore-8.0?view=aspnetcore-7.0#inject-keyed-services-into-components
