The list of referenced types contains more than one type with data contract name '{0}' in namespace '{1}'. Verify the list ...

The list of referenced types contains more than one type with data contract name '{0}' in namespace '{1}'. Verify the list of referenced assemblies for type reuse in the 'Advanced' dialog in 'Add Service Reference'. You need to exclude all but one of the following types. Only matching types can be valid references: {2}