Hi Duy,
The
RadWindow control does not have modal behavior by default, but in case that you set the
Modal property to "true" then you cannot interact with the parent page. In your case, I suppose that you used that property with value "true".
In case that you point the predefined dialogs(radalert...), you need to use the following approach (those dialogs are modal by default) :
I hope this information helps.
Regards,
Fiko
the Telerik team