.NET Framework thread "ancestry"

Question

I am looking for a way to determine for a thread on which other thread it was originally spawned. I do not know whether a mechanism exists to do this, similar to the "Parent" property on Tasks in the new Task Parallel Library for .NET 4

Edit: Further investigation actually seems to indicate that there is no location to store this information, so short of really ugly hacks this does not appear to be possible to implement transparently.

As such I think I will accept the sample code below as the most feasible (non-transparent) answer to solve the problem, even though I'll have to look for an alternate design myself. Thanks :)

Answer 1

The system doesn't provide such functionality internally. You can pass the thread ID of the parent thread to the thread start function pretty easily:

static class ThreadSpawner
{
    [ThreadStatic]
    private static int parentThreadId;
    public static int ParentThreadId
    {
        get { return parentThreadId; }
    }

    private class ThreadInfo
    {
        public int ParentId;
        public Action Method;
    }

    private static void StartThread(object parameter)
    {
        var threadInfo = (ThreadInfo)parameter;
        parentThreadId = threadInfo.ParentId;
        threadInfo.Method();
    }

    public static void Spawn(Action start)
    {
        new Thread(StartThread).Start(
            new ThreadInfo { 
                 Method = start, 
                 ParentId = Thread.CurrentThread.ManagedThreadId 
            });
    }
}


// Usage:
ThreadSpawner.Spawn(MyMethod);

static void MyMethod() { 
    Console.WriteLine(ThreadSpawner.ParentThreadId);
}

Answer 2

Worse, creating a .NET thread doesn't guarantee getting a native thread so you can't depend on being able to walk the thread parent information with P/Invoke either.

I know if you write test code you will see the native thread, but it's not required to generate it and on some conditions that are difficult to guess it won't.

EDIT: can't get thread parent via P/Invoke anyway.