HttpContextAccessor，IPrincipal和ServiceCollection

Question

有沒有一種方法可以實現下一個行爲？

public static void Configure(IServiceCollection services) { 
    services.AddScoped(typeof(Func<IPrincipal>), ???); 
    services.AddInstance(typeof(Func<IPrincipal>), ???); 
} 

1.不起作用：

Func<IServiceProvider, IPrincipal> getPrincipal = 
    (sp) => sp.GetService<IHttpContextAccessor>().HttpContext.User; 

services.AddScoped(
    typeof(Func<IPrincipal>), 
    getPrincipal); 

2.不起作用：

var builder = services.BuildServiceProvider(); 

services.AddInstance(
    typeof(Func<IPrincipal>), 
    builder.GetService<IHttpContextAccessor>().HttpContext.User); 

Answer 1

工作液：

Func<IServiceProvider, IPrincipal> getPrincipal = 
    (sp) => sp.GetService<IHttpContextAccessor>().HttpContext.User; 

services.AddScoped(typeof(Func<IPrincipal>), sp => { 
    Func<IPrincipal> func =() => { 
     return getPrincipal(sp); 
    }; 

    return func; 
}); 

Answer 2

Func<IServiceProvider, IPrincipal> getPrincipal = 
    (sp) => sp.GetService<IHttpContextAccessor>().HttpContext.User; 

services.AddScoped(
    typeof(Func<IPrincipal>), 
    getPrincipal); 

您正在試圖解決的委託，但我假設你想要解決IPrincipal。我假設您的服務可能如下所示

public class MyService : IMyService 
{ 
    public MyService(IPrincipal principal) 
    { 
     ... 
    } 
} 

如果是這樣，那麼您的註冊是錯誤的。您正在註冊Func<IPrincipal>，但預計未註冊IPrincipal。

您應該爲工廠註冊IPrincipal或（推薦不到的imho）將Func<IPrincipal>注入您的服務。

Func<IServiceProvider, IPrincipal> getPrincipal = 
    (sp) => sp.GetService<IHttpContextAccessor>().HttpContext.User; 

services.AddScoped<IPrincipal>(getPrincipal); 

或更短

services.AddScoped<IPrincipal>(
    (sp) => sp.GetService<IHttpContextAccessor>().HttpContext.User 
); 

或

public class MyService : IMyService 
{ 
    priate IPrincipal principal; 
    public MyService(Func<IPrincipal> principalFactory) 
    { 
     this.principal = principalFactory(); 
    } 
}