如何将Linq中的自定义类型映射到Sql？

I have a Customer class that contains a property, MyProperty, which is of a custom type MyCustomType. I want to persist the property value in the database as text. In the designer I've set the Type to 'MyType' and the Server Data Type to 'varchar(10)'. When I build the project I get the following error:I have a Customer class that contains a propert