WinAPI SetWindowPos not working for simple apps like notepad and calc

Question

I develop on Windows 10.

I want to move and resize an external application. I tried to make it work first with notepad and calculator. But, whatever I do the notepad/cal do not move or resize. I tried using SetWindowPos, UpdateWindow and MoveWindow but nothing worked. I debugged the code, and the inner part of the foreach does get executed.

I tried to run it as admin as suggested here, but it didn't help.

static void foo()
{    
    foreach (var p in Process.GetProcesses().Where(p => p.ProcessName.ToLower().Contains("calculatorapp")))
    {
        SetWindowPos(p.Handle, HWND.TopMost, 10, 10, 100, 300, (uint)(SWP.SHOWWINDOW));
        int err = Marshal.GetLastWin32Error();

        UpdateWindow(p.Handle);
        //SetWindowPos(p.Handle, 0, 0, 250, 250, true);
        MoveWindow(p.Handle, 0, 0, 250, 250, true);
    }
}

Answer 1

Just as Hans Passant said, you need a window handle like this.

HWND hwnd=(HWND)0x0xxxxxx;

I used SPY++ here to get the window handle of notepad. Then usedSetwindowpos to move the notepad to a new location and get the new size.