How do you modify your database after generating your DbContext?

Question

Now that i have generated 19 code-first classes from an existing database by:

• Creating a Model-First Entity, and choosing "Generate from database"
• Right clicking and choosing "Add Code Generation Item"
• EF 4.x DbContext Generater

All the classes i want are generated, and I'm very happy with them...

And now for my question(s)

• Why are they all the generated .cs files nested in a sealed .tt collection?
• Why can't i copy paste them out to any folder i like, and treat them like normal classes?
• Is it just me, or are you unable to use migrations "update-database" when you do it like that?

I guess my overall question is, why are they located in a .tt folder? And how shall i update my database now? By editing the database manually and then update the Model, and then generate the dbContext again? Or is there a trick to get .cs files out of a .tt folder?

How do you modify you database after generating your DbContext?

Answer 1

• Why are they all the generated .cs files nested in a sealed .tt collection?

Your code-first classes are not code-first classes. They were generated based on your database schema. Hence, this is a database-first approach. With database first, your entity classes are generated based on the database. In other words, the database comes first, the code comes second. The .tt file is a T4 template that decides how to generate your classes based on the database. You could change the database and then regenerate your entity classes.

• Why can't i copy paste them out to any folder i like, and treat them like normal classes?

Because they are generated files, based on the T4 template.

• Is it just me, or are you unable to use migrations "update-database" when you do it like that?

This part of your question I can't answer for certain, and will have to defer. However it seems to me like you want to mix and match approaches. It sounds like you want to start by generating code classes based on your database, and from there forward, change the database based on new entity classes you add to the model project. Is that right?

You can forgo the code-generation part and just go with a pure code-first approach, now that you have an idea of what the entity POCO's should look like. I have tried this T4 code generation before (pre EF 4.1) and immediately abandoned it, because as you have seen, since the entity and DbContext classes are generated, you lose control over the object-oriented model.