Get parent windows in a Word Add-In

If you need the parent window in a Word Add-In, you can't use FindWindow as the actual Word caption is not the title you set. It adds " - Microsoft Word" to it. If it is used in Outlook, it doesn't add anything. And if it's a non-English version of Word, it's something else.

So here is code that will find it. This is written in C# which added a couple of other wrinkles like passing a pointer to an int as the lParam:

  private const string CAPTION = "F076B0EA-FEE3-40E0-A576-4E68D13F57CA";

  /// <summary>
  /// Return the HWND of the parent app.
  /// </summary>
  /// <returns>The window handle.</returns>
  public static IWin32Window GetParentWindow(Application app)
  {
   string saveCaption = app.Caption;
   app.Caption = CAPTION;

   CallBack myCallBack = new CallBack(Report);
   IntPtr hwnd = (IntPtr)0;
   EnumWindows(myCallBack, ref hwnd);

   if (hwnd != (IntPtr)0)
   {
    app.Caption = saveCaption;
    return new HWnd(hwnd);
   }

   hwnd = (IntPtr) FindWindow("OpusApp", CAPTION);
   app.Caption = saveCaption;

   return new HWnd(hwnd);
  }

  private static bool Report(int hwnd, ref IntPtr lParam)
  {

   string lpText = new string((char) 0, 100);
   GetWindowText(new IntPtr(hwnd), lpText, lpText.Length);
   if (lpText.IndexOf(CAPTION) == -1)
    return true;

   // walk up the chain (never seen it actually happen)
   int par = hwnd;
   while (par != 0)
   {
    hwnd = par;
    par = GetParent(par);
   }

   lParam = (IntPtr)hwnd;
   return false;
  }

  private class HWnd : IWin32Window
  {
   private IntPtr _hwnd;
   public HWnd(IntPtr handle)
   {
    _hwnd = handle;
   }
   public IntPtr Handle
   {
    get { return _hwnd; }
   }
  }