How to Configure a Self Referencing Entity in Code First

Recently I was working on a project that required a categorization option. I wanted the user to have the option to create categories and as many subcategories as they wanted. To realize this I created a category model that was self referencing:

It’s important that you don’t forget the Foreignkey data annotation because otherwise you will get an error like this:

Unable to determine a valid ordering for dependent operations. Dependencies may exist due to foreign key constraints, model requirements, or store-generated values.

Further make sure that ParentId is nullable because it makes no sense if every category has a parent if it was even possible.

Alternative

Instead of using data annotations you can also use Fluent API to create a self referencing model. When you choose for this approach add the following code to your DbContext:

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