Question

I have codes written in native C++ that controls other processes (“client processes”) created by CreatePrcess() and other Windows APIs
Then client processes (console, single-thread) wait for the message MSG_OK from the “server” process and resume running when the message is received.
I used PostThreadMessage() and it worked fine.

int MSG_OK = RegisterWindowMessage("MSG_OK");
void run(TCHAR* path) {
    STARTUPINFO si={0,}; si.cb=sizeof(STARTUPINFO); si.dwFlags=0;
    PROCESS_INFORMATION pi;
    CreateProcess(NULL, path, NULL, NULL, FALSE, 0, NULL, NULL, &si, &pi);
    Sleep(1000); // Just for simplicity. Actual code is message-based
    PostThreadMessage(pi.dwThreadId, MSG_OK, 0, 0);
    CloseHandle(pi.hProcess);   // closing process handle makes usage count 1
    CloseHandle(pi.hThread);    
}

Now I’d like to rewrite the code in C#, using p/invoke’s as little as possible.
The following is the code I’m working on:

[return: MarshalAs(UnmanagedType.Bool)]
[DllImport("user32.dll", SetLastError = true)]
public static extern bool PostThreadMessage(uint threadId, int msg, IntPtr wParam, IntPtr lParam);

public void run(string path) {
    Process proc = new Process();
    ProcessStartInfo si = new ProcessStartInfo();
    si.FileName = path;
    proc.StartInfo = si;
    proc.Start();
    uint threadId; // <----?
    PostThreadMessage(threadId, MSG_OK, 0, 0);
    proc.Dispose();
}

I found C# classes such as Process and ProcessStartinfo but couldn’t find any member similar to dwThreadId. Is there any?

EDIT: Since the client process is a single thread app,

 proc.Threads[0].id

seems to be the threadId I’m looking for. Am I doing something wrong?

Answer 1

Please see this thread.

I would consider using some other approaches like mutexes, events or semaphores.