Question

Is it possible to call ShowDialog(), but to create dialog window under main form, not on the top?

I’m calling ShowDialog because I want to stop executing the main program.

I don’t need the dialog window, because I will create many dialogs from threads and they will prevent each other.

Answer 1

You need to read synchronization of threads. For stopping executing code use EventWaitHandle object.

Instead of creating and show dialog call WaitOne() of EventWaitHandle:

private static EventWaitHandle ev;
//...
[MTAThread]
public static void Main()
{
    //...
    ev = new EventWaitHandle(false, EventResetMode.ManualReset);
    //...
    ev.WaitOne(); //Stop execution
    //...
}

//Another thread function.
public static void ThreadProc()
{
    //...
    ev.Set(); //Continue execution of Main
    //...
}

A good example is on MSDN. Also note, that you need to call Reset() before using blocking again or create EventWaitHandle with EventResetMode.AutoReset option (read more on MSDN).