Get all window handles for a process

Question

Using Microsoft Spy++, I can see that the following windows that belong to a process:

Process XYZ window handles, displayed in tree form just like Spy++ gives me:

A
  B
  C
     D
E
F
  G
  H
  I
  J
     K

I can get the process, and the MainWindowHandle property points to the handle for window F. If I enumerate the child windows using I can get a list of window handles for G through K, but I can't figure out how to find the window handles for A through D. How can I enumerate windows that are not children of the handle specified by MainWindowHandle of the Process object?

To enumerate I'm using the win32 call:

[System.Runtime.InteropServices.DllImport(strUSER32DLL)]
            public static extern int EnumChildWindows(IntPtr hWnd, WindowCallBack pEnumWindowCallback, int iLParam);

Answer 1

Pass IntPtr.Zero as hWnd to get every root window handle in the system.

You can then check the windows' owner process by calling GetWindowThreadProcessId.

Answer 2

For everyone still wondering, this is the answer:

List<IntPtr> GetRootWindowsOfProcess(int pid)
{
    List<IntPtr> rootWindows = GetChildWindows(IntPtr.Zero);
    List<IntPtr> dsProcRootWindows = new List<IntPtr>();
    foreach (IntPtr hWnd in rootWindows)
    {
        uint lpdwProcessId;
        WindowsInterop.User32.GetWindowThreadProcessId(hWnd, out lpdwProcessId);
        if (lpdwProcessId == pid)
            dsProcRootWindows.Add(hWnd);
    }
    return dsProcRootWindows;
}

public static List<IntPtr> GetChildWindows(IntPtr parent)
{
    List<IntPtr> result = new List<IntPtr>();
    GCHandle listHandle = GCHandle.Alloc(result);
    try
    {
        WindowsInterop.Win32Callback childProc = new WindowsInterop.Win32Callback(EnumWindow);
        WindowsInterop.User32.EnumChildWindows(parent, childProc, GCHandle.ToIntPtr(listHandle));
    }
    finally
    {
        if (listHandle.IsAllocated)
            listHandle.Free();
    }
    return result;
}

private static bool EnumWindow(IntPtr handle, IntPtr pointer)
{
    GCHandle gch = GCHandle.FromIntPtr(pointer);
    List<IntPtr> list = gch.Target as List<IntPtr>;
    if (list == null)
    {
        throw new InvalidCastException("GCHandle Target could not be cast as List<IntPtr>");
    }
    list.Add(handle);
    //  You can modify this to check to see if you want to cancel the operation, then return a null here
    return true;
}

for WindowsInterop:

public delegate bool Win32Callback(IntPtr hwnd, IntPtr lParam);

for WindowsInterop.User32:

[DllImport("user32.dll")]
public static extern uint GetWindowThreadProcessId(IntPtr hWnd, out uint lpdwProcessId);

[DllImport("user32.Dll")]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool EnumChildWindows(IntPtr parentHandle, Win32Callback callback, IntPtr lParam);

Now one can simply get every root window by GetRootWindowsOfProcess, and their children by GetChildWindows.

Answer 3

You can use EnumWindows to get every top-level window, and then filter the results based on GetWindowThreadProcessId.