c# - HttpContextAccessor、IPrincipal 和 ServiceCollection

Question

有没有办法实现下一个行为？

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

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

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

您正在尝试解析委托(delegate)，但我假设您想要解析 IPrincipal反而。我假设您的服务可能看起来像这样

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>但期待 IPrincipal未注册。

您应该为 IPrincipal 注册工厂或(不太推荐恕我直言)注入(inject)Func<IPrincipal>为您服务。

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

services.AddScoped<IPrincipal>(getPrincipal); 

或更短的

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();
    }
}