Entity Framework 4 + DBContext T4 + Abstract Base Class

Question

I'm using EF 4.2 (database-first) with the DBContext T4 templates to create my POCO classes. This works very well, but now I stumpled over an issue with an abstract base class:

I need my T4 generated POCO class to inherit from a custom abstract class that has abstract properties:

//my abstract base class (shortened)
public abstract class BaseClass  {
    public abstract int? Property1 { get; set; }
    public abstract int? Property2 { get; set; }

    // a lot of methods that work with above properties
}

//my T4 generated entity (shortened)
public partial class Entity {
        public Nullable<int> Property1 { get; set; }
        public Nullable<int> Property2 { get; set; }
}

//and a partial class to make the T4 entity inherit from my abstract class
public partial class Entity : BaseClass {
}

My problem is that the compiler won't build this, because the properties in the T4 class are not marked as "override". LINQ 2 SQL had the option to change the inheritance modifier for an entity property, but I can't find this option in the EF Model Designer.

Is there a way to tell the EF Model Designer and the T4 templates to mark certain properties as override (I could, of course, change the generated C# code, but this changes would be overwritten when T4 runs again)? Is there any other way I can make this compile & work?

Thanks a lot, ~ saxx

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Update 1: Fixed a typo.

Answer 1

EF Model Designer offers no option to change the inheritence modifier. There are a few workarounds though.

1. Build a convention based system in your T4 model where you react differently (add override keyword) when the name of a property matches a certain pattern.
2. Use an interface rather than a baseclass and define logic in static classes/extension methods.
3. Rename the relevant properties in the EF designer and optionally, set their access modifier on private. Implement the abstract properties by making them reflect the renamed properties.