It was a mistake with access to Telerik data. They stopped supporting their visual designer. To fix the problem, you should get updated access to data from the NuGet Telerik.DataAccess package. Installing a new data access should provide you with Q2 2015 libraries. It will also add the package file to your project. You also need to open this and change the line
<UseXmlMapping Condition="'$(UseXmlMapping)'==''">false</UseXmlMapping> to <UseXmlMapping Condition="'$(UseXmlMapping)'==''">true</UseXmlMapping>
Also add the following code at the end of your property groups and before the element groups
<PropertyGroup> <UseXmlMapping>true</UseXmlMapping> </PropertyGroup>
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