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RadWindow Takes a Lot of Time to Open on IE, Especially 11


RadWindow Takes a Lot of Time to Open on IE, Especially 11.


DOM operations are slower in IE and initializing the Resize functionality may take some more time than expected when the page is heavy (e.g., even up to 300-400ms for the first time a RadWindow gets opened).


There are several ways to avoid this issue:

  • Use the Classic RenderMode. It uses a different resizing mechanism that does not get initialized separately.

  • Disable the Resize behavior of the RadWindow. You can do that by declaring different Behaviors (see the User Interaction With The Window article), or by removing it from the current set, e.g.:

    Behaviors="Move, Close, Maximize, Pin" 
    RadWindowManager1.Behaviors = WindowBehaviors.Default And Not WindowBehaviors.Resize 
    RadWindowManager1.Behaviors == WindowBehaviors.Default & ~WindowBehaviors.Resize 
  • Initialize the Resize behavior after showing the RadWindow:

    function openWindow() {
      var wnd = GetRadWindowManager().open();
      wnd.set_behaviors(wnd.get_behaviors() | Telerik.Web.UI.WindowBehaviors.Resize); //add the behavior again, if needed
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