Then edit your csproj, and add the following ItemGroup:
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<ItemGroup> <PageInclude="Properties\DesignTimeResources.xaml" Condition="'$(DesignTime)'=='true' OR ('$(SolutionPath)'!='' AND Exists('$(SolutionPath)') AND '$(BuildingInsideVisualStudio)'!='true' AND '$(BuildingInsideExpressionBlend)'!='true')"> <Generator>MSBuild:Compile</Generator> <SubType>Designer</SubType> <ContainsDesignTimeResources>true</ContainsDesignTimeResources> </Page> </ItemGroup>
Reload the project, and the XAML designer, and everything may now work…