Entity Framework Core creating model from existing database

Question

With Entity Framework Core, how do you generate the EF model and the entities?

According to ASP.NET Core - Existing Database Microsoft article you need to run a command like this one in the Package Manager Console:

Scaffold-DbContext "Server=(localdb)\mssqllocaldb;Database=Blogging;Trusted_Connection=True;" Microsoft.EntityFrameworkCore.SqlServer -OutputDir Models 

That gives you zero control on what tables or views to import. Is it possible that this is the only way to reverse engineer the database and create the EF models and entities now with EF Core and how is that progress when compared to the way this was done with full Entity Framework for years now?

Answer 1

I know this question is a bit old, but I think it's pretty useful for people stumbling over the same problem.

If I've understood your question correctly, you want to specify which Tables should be generated. It should be possible if you add the -Tables Parameter to the command.

Here is the command I used to generate 3 Tables of the Database (in Package-Manager Console):

Scaffold-DbContext "Server=(localdb)\mssqllocaldb;Database=DatabaseName;Trusted_Connection=True;"        -Provider Microsoft.EntityFrameworkCore.SqlServer       -OutputDir Models -Context NorthwndContext       -Tables Products,Categories,Suppliers -Force 

As you can see, I use the Northwnd-Database and only generate the tables "Products, Categories and Suppliers". Obviously, you can add more tables, you just have to separate them with commas.

If you don't know, you can get the DatabaseName by going to the Data Connections (Server Explorer), click on the Database you want to add and on the right side (Properties), you see a Property (Name). For me it was "NORTHWND.MDF".

I used -Force to override any Models I've already created.

You can use -DataAnnotations to get annotated models. Otherwise, you get Fluent model configuration.

PS: I've only tried this with ASP.NET Core 2 and Entity Framework Core 2.0.0.

Answer 2

My situation was that I had a .net 4.5+ class library with DbContexts in it.

Those DbContexts had been created from an existing DB using the "Code First from existing Database" Wizard. This Wizard seems to be missing from EF Core.

To create a new Code First DbContext from an existing DB compatible with EF Core, I loosely followed the guide here

My steps:

• Created a new Core Class Library

• Added the nuget package Microsoft.EntityFrameworkCore

• Added the nuget package Microsoft.EntityFrameworkCore.Tools
• Added the nuget package Microsoft.EntityFrameworkCore.SqlServer

• Added the nuget package Microsoft.EntityFrameworkCore.SqlServer.Design

• Opened the nuget Package Manager console

• Entered the command

  Scaffold-DbContext "data source=MYSQLDBSERVER\MYSQLINSTANCE;initial catalog=MYDB;integrated security=True;MultipleActiveResultSets=True;" 

• Entered as provider

  Microsoft.EntityFrameworkCore.SqlServer 

Please note that when using a non-Core project you might run into problems with the nuget Package Manager console. I avoided this problem by just creating a new Core Class Library, instead of a .net one.

Once you have created the context, you can edit it like normal in Code First, e.g. you can delete the tables you don't want to use.