使用Thread.CurrentPrincipal與異步和等待？

Question

考慮以下代碼，該代碼在單個執行主線程上設置ClaimsPrincipal，然后運行任務並嘗試訪問ClaimsPrincipal：

public class Program
{
    public static void Main(string[] args)
    {
        //Setting the CurrentPrincipal on the main thread
        Thread.CurrentPrincipal = new ClaimsPrincipal(new ClaimsIdentity(new[] { new Claim("name", "bob"), new Claim("role", "admin") }, "CUSTOM", "name", "role"));
        Console.WriteLine("Thread.CurrentThread.ManagedThreadId " + Thread.CurrentThread.ManagedThreadId);
        Console.WriteLine("Thread.CurrentPrincipal?.Identity?.Name " + (Thread.CurrentPrincipal?.Identity?.Name ?? "null"));

            AsyncHelper.RunSync(
            async () =>
            {
                Console.WriteLine("\tInside Async Method - Thread.CurrentThread.ManagedThreadId " + Thread.CurrentThread.ManagedThreadId);
                Console.WriteLine("\tInside Async Method - Thread.CurrentPrincipal?.Identity?.Name " + (Thread.CurrentPrincipal?.Identity?.Name ?? "null"));

                //Simulate long(er) running work
                await Task.Delay(2000);

                Console.WriteLine("\tInside Async Method - Thread.CurrentThread.ManagedThreadId " + Thread.CurrentThread.ManagedThreadId);
                Console.WriteLine("\tInside Async Method - Thread.CurrentPrincipal?.Identity?.Name " + (Thread.CurrentPrincipal?.Identity?.Name ?? "null"));
            });

        Console.WriteLine("Thread.CurrentThread.ManagedThreadId " + Thread.CurrentThread.ManagedThreadId);
        Console.WriteLine("Thread.CurrentPrincipal?.Identity?.Name " + (Thread.CurrentPrincipal?.Identity?.Name ?? "null"));
    }
}

和

internal static class AsyncHelper
{
    private static readonly TaskFactory MyTaskFactory = new
        TaskFactory(CancellationToken.None,
            TaskCreationOptions.None,
            TaskContinuationOptions.None,
            TaskScheduler.Default);

    public static void RunSync(Func<Task> func)
    {
        AsyncHelper.MyTaskFactory
                .StartNew<Task>(func)
                .Unwrap()
                .GetAwaiter()
                .GetResult();
    }
}

該程序的輸出是

Thread.CurrentThread.ManagedThreadId 2
Thread.CurrentPrincipal?.Identity?.Name bob
        Inside Async Method - Thread.CurrentThread.ManagedThreadId 3
        Inside Async Method - Thread.CurrentPrincipal?.Identity?.Name null
        Inside Async Method - Thread.CurrentThread.ManagedThreadId 3
        Inside Async Method - Thread.CurrentPrincipal?.Identity?.Name null
Thread.CurrentThread.ManagedThreadId 2
Thread.CurrentPrincipal?.Identity?.Name bob
Press any key to exit

我以為我會看到的是：

Thread.CurrentThread.ManagedThreadId 2
Thread.CurrentPrincipal?.Identity?.Name bob
        Inside Async Method - Thread.CurrentThread.ManagedThreadId 3
        Inside Async Method - Thread.CurrentPrincipal?.Identity?.Name bob <--- Notice here
        Inside Async Method - Thread.CurrentThread.ManagedThreadId 3
        Inside Async Method - Thread.CurrentPrincipal?.Identity?.Name bob <--- Notice here
Thread.CurrentThread.ManagedThreadId 2
Thread.CurrentPrincipal?.Identity?.Name bob
Press any key to exit

在主線程上設置的ClaimsPrincipal發生了什么（在此特定輸出ManagedThreadId 2的情況下）？ 為什么在復制ExecutionContext時沒有將ClaimsPrincipal復制到另一個線程？

更新 ：.Net目標框架是.NET Core 2.0。

更新2 ：此問題似乎特定於.NET Core。 使用相同的代碼，但針對.NET 4.6.1框架，我得到了期望的輸出。

Answer 1

您只是不能依賴線程屬性，因為諸如為任務分配線程之類的細節取決於具體的ThreadScheduler（ https://msdn.microsoft.com/zh-cn/library/system.threading.tasks.taskscheduler ( v= vs.110）.aspx ）。 有許多不同的ThreadScheduler實現。

有一個實現您自己的自定義TaskScheduler的選項，您可以在其中將Thread.CurrentPrincipal設置為您的值，但更好的是，不要完全依賴所有線程屬性，而這些屬性始終處於“任務級別”。