HttpContextAccessor，IPrincipal和ServiceCollection

Question

有没有办法实现下一步行为？

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); 

您正在尝试解析该委托，但我认为您想要解决IPrincipal。我认为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或（少推荐的imho）注册工厂，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();
    }
}

Answer 2

工作解决方案：

var localFolder = Windows.Storage.ApplicationData.Current.LocalFolder;
var file = await localFolder.CreateFileAsync("temp.png", CreationCollisionOption.ReplaceExisting);
using (var ras = await file.OpenAsync(FileAccessMode.ReadWrite, StorageOpenOptions.None))
{
     WriteableBitmap bitmap = imageSource;
     var stream = bitmap.PixelBuffer.AsStream();
     byte[] buffer = new byte[stream.Length];
     await stream.ReadAsync(buffer, 0, buffer.Length);
     BitmapEncoder encoder = await BitmapEncoder.CreateAsync(BitmapEncoder.PngEncoderId, ras);
     encoder.SetPixelData(BitmapPixelFormat.Bgra8, BitmapAlphaMode.Straight, (uint)bitmap.PixelWidth, (uint)bitmap.PixelHeight, 96.0, 96.0, buffer);
     await encoder.FlushAsync();
}