Using EF Core in a Separate Class Library project

Entity Framework Core is an Object Relational Mapper (ORM) for Core projects. It’s. really easy to use and you can get up and running with it really quickly.

That being said it does have some quirks and idiosyncracies which may catch you off guard if you’re not aware of them. I have found keeping an eye on Julie Lermans blog really helps, she seems to have a knack for find ing the edge cases and solutions when it comes to Entity Framework in general.

In the particular example I want to highlight in this blog post, is something I uncovered when developing my series of blogs post, regarding developing an Core API for my Stop Web Crawlers WordPress Plugin.

I wanted to keep my Database layer was seperate from API logic, in that I didn’t really want to include my Database Enity classes etc within my API code. Potentially I will be developing a further two micro service type API’s which may use the same Database Schema but not necessarily the same database server.

Can’t wait to see it in action ?

Check out the code on GitHub


Add Database Class Library Project

We make use of solution and projects files in the source code, so if you are not familiar with working with solution files using .net core you may want to check out my post – Creating and Editing Solutions files with .net core CLI.

I’ll add a new class library project, primary purpose of this project is to create Database Context object which well share across a couple of projects.

Rename the generated class to ApiContext.cs

We’ll also add a reference to Microsoft.EntityFrameworkCore We’ll also add some code to create a barebones Database Context

Database Entities

We’ll now create a new project which we’ll use to create a Database Entity objects we’ll call it rather unimaginetively Api.Database.Entity.

The default class created via the project template we’ll rename to BaseEntity.cs and we’ll add some basic entity properties we need.

We’ll also add an additional folder to the Entity Project and call it Threats. We’ll also create 3 additional classes Status.cs , Threat.cs, ThreatType.cs. To View the properties of the file check the source code repository

Add Reference to Entity

We now need to add a reference for our Entity Project project to the Database Project.

Create Portal COre Library

For the purpose of my project I will create another separate class library project, which I will call Portal.Core, the purpose of the this library will be to central library for common functions, Modules or Global variables etc required across the multiple projects.

We’ll rename the generated class to SchemaName.cs and we will add constant string value of Portal

We need to add 2 new Addtional Nuget Packages to the Api.Database.csproj

  • Microsoft.EntityFrameworkCore.Design
  • Microsoft.EntityFrameworkCore.Tools.DotNet

We are now ready to update, ApiContext.cs with additional logic

Our EF Core work is now complete. We have a basic Schema, and we have developed our Context, for the most part we are done. All we need to do now is create the Migration to get our Database up and running.

I will illustrate how we will make use of SQL Server 2016, running within a Docker Container to enable testing of the Migration Scripts. I won’t discuss how to get started with SQL Server and Docker. Microsoft do a pretty good job of explaining Connect to SQL Server on Linux

Once you have your SQL Server up and running whichever way you choose. We will need to create another DummyUI console project. The reason for this is a little quirk in how EF Core works, is that you are unable run Migrations against Class Library projects. We will create a Dummy Console Poject, that will be used as the Start Up project for the Migration task.

We will need to add a couple of references to the DummyDB

  • Microsoft.EntityFrameworkCore
  • Microsoft.EntityFrameworkCore.Design
  • Microsoft.EntityFrameworkCore.Tools.DotNet

We also need to add project references to our Api.Database & Api.Database.Entity

We need to add an Additional class to our Api.Database pjoject


The process of creating a Migration is as follows:

Open the Terminal and navigate to the folder containing Api.Database.csproj
so right clicking on the project and Selecting Open Command line

Then using dotnet ef --startup-project ../DummyDB migrations add [Migration Name]

will initiate the migrations
When setting up an EF Core project ensure the the CSproj file has the following references

Add reference the EF Library

In order to make use of our seperate library we will need to edit the StartUp.cs to add our Context to the Services Collection.

In my case I am making use of Microsoft SQL Server, so I will also need to add Nuget Package Microsoft.EntityFrameworkCore.SqlServer and Microsoft.EntityFrameworkCore.SqlServer.Design to the Api Project.

I will follow up in subsequent posts on how to ensure your DB is seeded etc.

Gary Woodfine

Helps businesses by improving their technical proficiencies and eliminating waste from the software development pipelines. A unique background as business owner, marketing, software development and business development ensures that he can offer the optimum business consultancy services across a wide spectrum of business challenges.

  • Jonathan Nungaray

    Thanks for the post! but How can we integrate this with the api project?

    • Jonathan, thank you for question.
      I now realise this may be glaring omission from my post. I will update it shortly.

      Essentially it is the same way you would using standard EF, you add a reference and Inject the Context.
      I will provide details in the update.

      • Jonathan Nungaray

        Yes thanks!, I already did it, was a little tricky since I am using simple injector instead the native one

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  • manu

    Gary, Can you give me tips to do this process using EF Core Database First approach? Using Microsoft docs site, I can generate the entities only in the same folder, but not in a different project library. Needs to separate Entities and EF DB libraries. Thanks

    • Manu, I haven’t actually tried this as I am away from a .net dev enviornment but I believe you should be able to do something similar too

      Scaffold-DbContext -Connection
      “‘[your connection string]” -Provider
      “Microsoft.EntityFrameworkCore.SqlServer” -OutputDir “Models” -Context
      “DbContext” –verbose

      Remember just to navigate to your project folder. If I have time this week, I may write a blog post explaining and a sample.
      Hope tthis Helps

      • manu

        Thanks for the suggestion. I tried with -Project option which will generate entities in a different project and -OutputDir option which will generate in a different folder, and both are working. However, I face difficulty in trying to add BaseEntity class inheritance reference while generating these new classes. I would like these models to avoid reference to EF namespace references and should be just POCO objects.