How to seed your EF Core database

Using Entity Framework Core as an Object Relation Mapper (ORM) for your Core Web or API projects, is really easy and you can be up and running with it really quickly.

I have previously discussed how to use EF Core in a seprate class library project and how to configure migrations to enable the update of your database schema.

Can’t wait to see it in action ?

Check out the code on GitHub



Although we have created a separate class library project for our EF Core database context class, ApiContext, we are going to develop some extension methods to this class but we are going to add this extension class to our main Api project.

The primary reason being that our Api.Database project is generic mini database project that is going to used for several disconnected micro service applications internally. Each of these micro service applications may have different database seeding requirements and therefore we want to be able to control the seeding on a per project basis.

Add Extension class

Add a new class to the root of the Api project and name it DbContextExtension.cs and add the following code.

We have added a simple boolean method we will call to determine whether all migrations have been applied.

Add Folder for data seeding scripts

Add a folder that will contain your data seeding scripts. This fodler will contain some JSON files which will contain the data required by the applicaiton.

I have just added a folder and called it seed. I have added three JSON files, threats.json , status.json & types.json

Add Seeding Extension Methods

We need to import a few additional namespaces to the DbContextExtension.cs

Add and addtional extension method to the DbContextExtension.csclass, that will be responsible for reading the data from the JSON files and the inserting to the database.

Modify StartUp.cs

We now need to add some code to the StartUp.cs to the Configure method


The above techniques illustrate how it easy it is to make use of Entity Framework core to create a database and seed it with the default data that it requires.

We used standard JSON data as a source for our data. We also made use of EF Core functions to insert the data.

Gary Woodfine

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  • Lê Trần Nguyên Lam

    My EnsureSeeded seems never get run. I place breakpoint but it’s skipped…

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  • Nik Godro

    thank you very much!…. There’s so many wrong “solution” out there about seeding in Core 2.0 following this error:
    Unable to create an object of type ‘LibraryContext’. Add an implementation of ‘IDesignTimeDbContextFactory’ to the project, or see for additional patterns supported at design time.
    You should add it to your description!
    You’ll be more view-able in search + more click = more view-able + ..= … + ..= …. anyway thanks a lot!