Ggtcf

I've created an MVC application. I would like to now add a new class-library project to the solution, and then add an EDMX file to that project.

This used to be easy. But now I have to choose between .NET Core and .NET Standard. But it appears it doesn't matter which I choose because if I create a class library with either of these frameworks, Visual Studio provides no option for adding an EDMX file to them! And I don't see an option to add a standard .NET Frameworks class library.

So what is the secret incantation to add a new project to my MVC solution, and then add an EDMX file to that project?

Note: I do have the option of adding an EDMX file directly to the MVC project. But I would prefer to place it in a separate project, which I've done before.

EDMX file is deprecated with EF Core and I believe it has been removed from .net core projects as well.
If you need to do that, you may need to add it to a normal .net 4.5 project and copy the files but this will make no sense using it with .net core or .net standard.

You should be using Code First anyway as it is cleaner and easier to use.

If you already have the database, you can refer to this link, it can help you to scaffold the classes from the database

https://docs.microsoft.com/en-us/ef/core/get-started/aspnetcore/existing-db

@Jonathan: The EDMX file is old way of doing things. EDMX is nothing but a T4 template which facilitates in creation of edmx.

With .Net Core the best way is to:
1. Create a .net core library project. Add entityframeworkcore nuget package from here
2. The use this link, to generate your model's from DB

The concept of EDMX is not supported anymore.

Hope this helps.

Based on your description you're using the old ASP.NET MVC framework, and not the new Core one, and in this case you're using the Full .NET framework. So, when you create the new Class Library project, you should do it with the Full .NET Framework, because .NET Core and .NET Standard does not support, EDMX. If you chose this one, you can add your ADO.NET Entity Data model to it:

At least for EF v6, if your using EF Migrations, each ('state'/'target') snapshot of the database (stored within the migrations-history db table & migration file) is an EDMX file just waiting to be decoded, saved to a file, and then loaded in VS (Visual Studio). ;)

It's a little in-depth (or at least challenging), but 'System.Data.Entity.Migrations.Edm.ModelCompressor' may present the clue.

Basically, you can extract the EDMX from one/the relevant migration. But I do agree that the Code-First approach should be used for the implementation, the EDMX is only a development-aid these days.