Using Data Annotations with an EDMX Model

It’s easy to apply data annotations to your class and then use that class with Entity Framework thanks to Code First, but what if you are using the Entity Data Model designer to create your Database First or Code First model and then relying on code generation to create your classes? There’s no opportunity to apply Data Annotations to your properties. You might modify the T4 template to apply Data Annotations that follow very common patterns in your classes, but typically this is not the appropriate mechanism for applying property-by-property attributes.

The generated classes are partial classes, which does give you the ability to add more logic to the classes with additional partial classes. However, you cannot add attributes in one partial class to properties that are declared in another partial class.