One or more selected items contain a data type that is not supported by the designer
One or more of the items dragged from Server Explorer/Database Explorer onto the O/R Designer contains a data type that is not supported by the O/R Designer (for example, CLR User-Defined Types (ADO.NET)).
To correct this error
Create a view that is based on the desired table and that does not include the unsupported data type.
Drag the view from Server Explorer/Database Explorer onto the designer.