Unfortunately the IlMerge
tool can't work with WPF assemblies properly as noted in the product page of the tool - http://research.microsoft.com/en-us/people/mbarnett/ilmerge.aspx
"Merging WPF assemblies
ILMerge is not able to merge WPF assemblies. They contain resources with encoded assembly identities. ILMerge is unable to deserialize the resources, modify the assembly identities, and then re-serialize them. Sorry! "
However, as Telerik now provides no-xaml assemblies, you can use the IlMerge tool to merge multiple Telerik WPF no-xaml assemblies into one and then reference the merged assembly in your solution. With this approach, you'll have to keep in mind that the assemblies don't specify any style resources so you'll have to use an implicit styles approach similarly to the ones described in this tutorial. Also, please make sure to update the alias of the Telerik namespaces in the style files/ResourceDictionaries as by default they come from the Telerik assemblies and as soon as you merge the assemblies toghether, you'll have to change namespace definitions accordingly.
Still, using IlMerge to merge our assemblies along with a WPF project exe file doesn't work. And the reason is in the IlMerge implementation as described in the tool product information. And if this is your goal, you'll have to use another tool or follow the workarounds suggested by the IlMerge authors:
I hope this information helps.
All the best,
the Telerik team