X Already contains a definition Y with EntityFramework? (simple database)

Question

I have 3 tables in my MS SQL database and I have added a EntityFramework(latest) to my project where I have imported these 3 tables. The first problem was that no Entities w

Answer 1

1. Right Click the Entity model.
2. Go to properties and remove the default name in the "Custom Tool".
3. Assign the edmx in the model.tt and model.context
4. Build and execute it you will be free from error.

Answer 2

You should either use None code generation strategy for your .edmx file. Or remove MainModel.tt and MainModel.Context.tt templates, which generate model entities and context.

If you use Default code generation strategy, then entities and context will be generated into MainModel.Designer.cs file. That would be standard entities, inherited from EntityObject, context will be inherited of ObjectContext. With Entity Framework 5 we have POCO entities generation. And whole generation is done in T4 templates, which generate context, inherited from DbContext, and POCO entities without some base type (well, object only).

When you have both templates and enabled code generation in edmx designer, then two sets of entities will be generated. That's why you have names conflict.