The restriction zone must be a static element on the page with explicit dimensions set in pixels. The main reason for this is that if this requirement is not met it can change its size and/or position. The problem with this change is that we cannot be notified about is in order to take some action with the RadWindows. Even if there was an event fired by the browser what would be the expected behavior for the RadWindows - to center again? To move to (0,0)? Something else? In all cases they would change without the user doing it which would be perceived as a bug. Yet another problem is the fact that a dynamic zone may become insufficient to contain its RadWindows which is not a valid case and the developer must make sure that the zone can contain at least the original dimensions of the RadWindows that are opened.
All that being said - recently there have been some improvements on this functionality that allow it to handle better some invalid scenarios, yet they should still be avoided and the requirement that the zone must be static, must have size in pixels and must not scroll is still in effect. Thus, I advise that you upgrade to the latest version of the controls.
With regard to MVC - please keep in mind that not everything from the Telerik RadControls for ASP.NET AJAX suite is supported in the MVC environment, because the frameworks are different and the RadControls for ASP.NET AJAX depend on the page lifecycle the WebForms engine provides.
What I can also suggest is that you set the KeepInScreenBounds property to true - it will return any RadWindow dragged outside of the viewport back inside.
You may also find useful the native MVC RadWindow extension we offer, for more details you can check out this demo
the Telerik team
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