How to make a Base Window class

I have a WPF form . I need to make it as a Base Window class. My WPF form having UI controls which is in XAML code as in any WPF form. How can I bind that XAML to my base class. I tried to use "ResourceDictionary" as a tempalte for the base window class. When I put my UI into a resource dictionary I found no way to open and see my UI in the design mode. Can anyone help me on this.