Action.BeginInvoke和Thread.CurrentPrincipal

Question

我知道System.Threading.Thread.CurrentPrincipal会在.Net 4.0+中进行大多数异步调用。但是，看起来它在调用AsyncResult回调之前被重置。我知道在这个特殊情况下我需要改变什么来解决它，但我想知道为什么框架在这里做（而不是在调用AsyncResult回调之后）。

作为第二个问题 - AsyncResult回调是否总是在＆＃34; work＆＃34;的同一个线程上运行。被执行了，或者这不保证？

System.Threading.Thread.CurrentPricipal = CustomPrincipal;
//ManagedThreadID is 101 (for example)
Promise.When(() => {
    //System.Threading.Thread.CurrentPrincipal still Custom Principal
    //As expected

    //ManagedThreadID is 254 (for example - a different thread, as expected)
}); 

public static IPromise<T> When<T>(Func<T> action)
{
    //System.Threading.Thread.CurrentPrincipal still CustomPrincipal
    //As expected
    Promise<T> p = new Promise<T>();
    action.BeginInvoke((result) =>
    {
        //System.Threading.Thread.CurrentPrincipal NOT CustomPrincipal (it's now a GenericPrincipal object) - reset by framework?
        //ManagedThreadId is still 254 (as expected)
        try
        {
            p.Complete(action.EndInvoke(result));
        }
        catch (Exception ex)
        {
            p.Complete(ex);
        }
    }, null);
    return p;
}