使用Thread.CurrentPrincipal与异步和等待？

Question

考虑以下代码，该代码在单个执行主线程上设置ClaimsPrincipal，然后运行任务并尝试访问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();
    }
}

该程序的输出是

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

我以为我会看到的是：

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

在主线程上设置的ClaimsPrincipal发生了什么（在此特定输出ManagedThreadId 2的情况下）？ 为什么在复制ExecutionContext时没有将ClaimsPrincipal复制到另一个线程？

更新 ：.Net目标框架是.NET Core 2.0。

更新2 ：此问题似乎特定于.NET Core。 使用相同的代码，但针对.NET 4.6.1框架，我得到了期望的输出。

Answer 1

您只是不能依赖线程属性，因为诸如为任务分配线程之类的细节取决于具体的ThreadScheduler（ https://msdn.microsoft.com/zh-cn/library/system.threading.tasks.taskscheduler ( v= vs.110）.aspx ）。 有许多不同的ThreadScheduler实现。

有一个实现您自己的自定义TaskScheduler的选项，您可以在其中将Thread.CurrentPrincipal设置为您的值，但更好的是，不要完全依赖所有线程属性，而这些属性始终处于“任务级别”。