In the common case RadMap doesn't need Telerik.Windows.Data assembly. The map control is using the assembly only in a scenario where the DataMappings
collection of the layer is populated. RadMap will work properly even without the Telerik.Windows.Data dll. However, if you decide to use the DataMappings collection I recommend you to include the Data dll.
Basically, the Telerik.Windows.Data assembly contains classes used in data scenarios (data binding helpers, custom collections, etc.) and some of our controls requires them. So, if you are using other controls (different than RadMap) from the DataVisualization dll we recommend adding also the Data assembly.
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