c# - Block closing WPF window (from a different thread) if OpenFileDialog is open -

to clear things before mention obvious choice, calling showdialog , not show method!!!

i block close (invoked different thread) off wpf window if openfiledialog open.

here code have (reduced show problem):

public class foowindow : window {     public foowindow()     {         initializecomponent();         this.closing += onclosing;         }      public void opendialogandcloseme()     {         var ofd = new openfiledialog();          thread th = new thread(() => closeme());         th.start();          ofd.showdialog(this);     }      public void closeme()     {         system.threading.thread.sleep(2000); //give openfiledialog time pop up...          //since method gets called different thread invoke it...         this.dispatcher.invoke(() => this.close());     }      private void onclosing(object sender, canceleventargs e)     {         //check if openfiledialog still open , block close...         e.cancel = true;     } } 

the problem facing onclosing part, how openfiledialog (or other dialog in case).

i have searched web , found win32 methods like:

[dllimport("user32")] [return: marshalas(unmanagedtype.bool)] private static extern bool enumchildwindows(intptr window, enumedwindow callback, arraylist lparam);  [dllimport("user32.dll", entrypoint = "findwindowex", charset = charset.auto)] static extern intptr findwindowex(intptr hwndparent, intptr hwndchildafter, string lpszclass, string lpszwindow); 

i have tried them both return 0 children, ideas what's going wrong?

here full code tried far:

//replace above onclosing implementation... 3 return false private void onclosing(object sender, canceleventargs e) {     //check if openfiledialog still open , block close...     var hwnd = new windowinterophelper(this).handle;      if (windowhandling.getchildren(hwnd).any())         e.cancel = true;      if (windowhandling.getchildrenv2(hwnd).any())         e.cancel = true;      if (windowhandling.getchildrenv3(hwnd).any())         e.cancel = true; }  public static class windowhandling {     private delegate bool enumedwindow(intptr handlewindow, arraylist handles);      [dllimport("user32")]     [return: marshalas(unmanagedtype.bool)]     private static extern bool enumchildwindows(intptr window, enumedwindow callback, arraylist lparam);      [dllimport("user32.dll", entrypoint = "findwindowex", charset = charset.auto)]     static extern intptr findwindowex(intptr hwndparent, intptr hwndchildafter, string lpszclass, string lpszwindow);      private static bool getwindowhandle(intptr windowhandle, arraylist windowhandles)     {         windowhandles.add(windowhandle);         return true;     }      public static ienumerable<intptr> getchildren(intptr hwnd)     {         if (hwnd == intptr.zero)             return enumerable.empty<intptr>();          var x = new windowhandleinfo(hwnd);         return x.getallchildhandles();     }      public static ienumerable<intptr> getchildrenv2(intptr hwnd)     {         var windowhandles = new arraylist();         enumedwindow callbackptr = getwindowhandle;         enumchildwindows(hwnd, callbackptr, windowhandles);          return windowhandles.oftype<intptr>();     }     public static ienumerable<intptr> getchildrenv3(intptr hparent)     {         var result = new list<intptr>();         var ct = 0;         var maxcount = 100;         var prevchild = intptr.zero;          while (true && ct < maxcount)         {             var currchild = findwindowex(hparent, prevchild, null, null);             if (currchild == intptr.zero)                 break;              result.add(currchild);             prevchild = currchild;             ++ct;         }          return result;     }      //http://stackoverflow.com/questions/1363167/how-can-i-get-the-child-windows-of-a-window-given-its-hwnd     private class windowhandleinfo     {         private delegate bool enumwindowproc(intptr hwnd, intptr lparam);          [dllimport("user32.dll", setlasterror = true)]         [return: marshalas(unmanagedtype.bool)]         private static extern bool enumchildwindows(intptr window, enumwindowproc callback, intptr lparam);          private readonly intptr _mainhandle;          public windowhandleinfo(intptr handle)         {             _mainhandle = handle;         }          public ienumerable<intptr> getallchildhandles()         {             var childhandles = new list<intptr>();              var gcchildhandleslist = gchandle.alloc(childhandles);             var pointerchildhandleslist = gchandle.tointptr(gcchildhandleslist);              try             {                 var childproc = new enumwindowproc(enumwindow);                 var x = enumchildwindows(this._mainhandle, childproc, pointerchildhandleslist);                 if (x == false)                 {                     var error = marshal.getlastwin32error();                 }             }                         {                 gcchildhandleslist.free();             }              return childhandles;         }          private static bool enumwindow(intptr hwnd, intptr lparam)         {             var gcchildhandleslist = gchandle.fromintptr(lparam);              if (gcchildhandleslist.target == null)                 return false;              var childhandles = gcchildhandleslist.target list<intptr>;             if (childhandles != null)                 childhandles.add(hwnd);              return true;         }     } } 

you can solve boolean value tracking if it's open or not:

bool dialogopen = false;  public void opendialogandcloseme() {     var ofd = new openfiledialog();      thread th = new thread(() => closeme());     th.start();      dialogopen = true;     ofd.showdialog(this);     dialogopen = false; }   private void onclosing(object sender, canceleventargs e) {     //check if openfiledialog still open , block close...     if(dialogopen)     {         e.cancel = true;     } }