That work only if you open webdialogwindow client side, if you open web dialog window server side does not work.

Tony,

Thanks for the quick fix, it works perfectly !!!

I can now plan to use the new WebDialog in my current develpment. If you discover more about this behaviour, I would be interested in hearing

Thanks again for the quick reply.

$IG.DialogMoveBehavior.prototype._doZ=
function(lid, elem, lidZ)
{
    this._newZ = this._oldZ = $util.getStyleValue(null, 'zIndex', elem);
    if(!lidZ)
        lidZ = $util.toInt($util.getStyleValue(null, 'zIndex', lid), 0);
    if(lidZ < 10)
        lid.style.zIndex = lidZ = 100; //z-index will default to 100 in a modal scenario
    if($util.toInt(this._oldZ, 0) <= lidZ)
        elem.style.zIndex = this._newZ = lidZ + 1;
    return lidZ;
};

}

Check the z-index of the dialog (and the dropdown or menu).  The dialog needs to display 'on top' of everything, so it's given an enormously high default z-index.  The dropdown portion of any non native dropdown control is an absolutely positioned container which also must get displayed above everything else.  It sounds like the Dialog Window is set to a z-index which is higher than the dropdown portion of the webcombo and webdatechooser (which I think use 1000).  Choosing which control ultimately displays on top is a matter of setting the z-index. The reason the classic HTML Select 'works' is because it's a native control to the browser which is actually a separate window.  Ever try to get an HTML element to appear over top of the HTML Select.. ?  Not fun.  virtually impossible without a buch of messy hacks. 

Anyway, to remedy your scenario you'll want to set the DialogWindow's z-index to a value lower than the dropdown, or set the dropdown's z-index higher than the DialogWindow.  Both can be set using the controls css class, and the z-index property.  I'll check with the product team and see if there's a reason we can't default this to something that will work better with other controls without forcing you to manually adjust the z-index. 

 -Tony