We remade big part of RadWindow and decided that this is the correct way to do things. Previously when RadWindow was declared in XAML we were removing it from its Parent and put it in a popup then show it. Clients tend to bind elements in the window to another XAML element and this binding getting broken and there were also other problems like panels layout is refreshed because of removing the window etc...
We believe that it is better practice to either create RadWindow in code behind or use it as a root element of a UserControl especially in WPF as there it is supposed that new windows are always root elements. So that is the reason that we changed the way RadWindow works when declared in XAML.
We are sorry for the caused inconvenience. Let us know if you have further questions.
@OrchidERP-- Could you provide some more info on the window disappearing on maximize.
the Telerik team
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