|Visual Studio version
I found an overlaping RadTabControl style example on these forums. But it had two issues:
1.) The initial Z-Order of the tab on load was incorrect.
2.) I wanted a style with the overlap on the left side, not the right as the example showed.
Using a style I improved upon from here, based on the standard Silverlight TabControl (See comments for my version):
I built up a version for the RadTabControl. The project is built/tested using the 2010 Q2 release of the Silverlight Telerik Suite for Silverlight 4.
It has a behavior that sets the proper ZIndex on tab items on selection / load, which requires the Blend Behavior SDK dlls. The SDK can be downloaded from here:
Since I needed a negative margin only on susequent tabs (not the first) I built up a proxy helper and converter to set margins based on the current tab index.
The example implements the style via intrinsic styles, so once the styles are imported into your resource dictionary, no additional work is needed.