HttpContextAccessor，IPrincipal和ServiceCollection

Question

有没有一种方法可以实现下一个行为？

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); 

您正在试图解决的委托，但我假设你想要解决IPrincipal。我假设您的服务可能如下所示

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

如果是这样，那么您的注册是错误的。您正在注册Func<IPrincipal>，但预计未注册IPrincipal。

您应该为工厂注册IPrincipal或（推荐不到的imho）将Func<IPrincipal>注入您的服务。

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(); 
    } 
}