gistfile1.txt

public class WindowHook : WindowProcHook
{
    static readonly Queue<Action> actionQueue = new Queue<Action>();
    static readonly Queue<Delegate> delegateQueue = new Queue<Delegate>();
    static readonly Queue<object> returnValueQueue = new Queue<object>();

    public enum UserMessage
    {
        ProcessMessage = 400,
    }

    [DllImport("user32.dll")]
    public static extern int SendMessage(IntPtr hWnd, int wMsg, IntPtr wParam, IntPtr lParam);
    [DllImport("kernel32.dll")]
    static extern uint GetCurrentThreadId();

    public WindowHook(IntPtr handle) : base(handle, "hooker")
    {
    }

    public void RunOnMainThread(Action action)
    {
        if (GetCurrentThreadId() == System.Diagnostics.Process.GetCurrentProcess().Threads[0].Id)
        {
            action();
            return;
        }

        this.Invoke(UserMessage.ProcessMessage);
        actionQueue.Enqueue(action);
    }

    public T RunOnMainThread<T>(Func<T> function)
    {
        try
        {
            if (GetCurrentThreadId() == System.Diagnostics.Process.GetCurrentProcess().Threads[0].Id)
                return function();

            delegateQueue.Enqueue(function);
            this.Invoke(UserMessage.ProcessMessage);
            return (T)returnValueQueue.Dequeue();
        }
        catch (Exception e)
        {
            return default(T);
        }
    }

    protected override IntPtr OnWndProc(IntPtr hWnd, int msg, IntPtr wParam, IntPtr lParam)
    {
        // ReSharper disable once SwitchStatementMissingSomeCases
        switch ((UserMessage)msg)
        {
            case UserMessage.ProcessMessage:
                while (actionQueue.Count > 0)
                    actionQueue.Dequeue()?.Invoke();
                while (delegateQueue.Count > 0)
                {
                    var invokeTarget = delegateQueue.Dequeue();
                    returnValueQueue.Enqueue(invokeTarget?.DynamicInvoke());
                }
                return IntPtr.Zero;
        }

        return base.OnWndProc(hWnd, msg, wParam, lParam);
    }

    public void Invoke(UserMessage msg)
    {
        SendMessage(this.Handle, (int)UserMessage.ProcessMessage, IntPtr.Zero, IntPtr.Zero);
    }
}