Fixing EF Core Model-Table Name Mismatches with Foreign Keys in Entity Framework

Learn how to resolve issues in Entity Framework Core when your model names differ from table names, particularly when handling relationships.
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This video is based on the question https://stackoverflow.com/q/66436453/ asked by the user 'briddums' ( https://stackoverflow.com/u/260473/ ) and on the answer https://stackoverflow.com/a/66437094/ provided by the user 'atiyar' ( https://stackoverflow.com/u/446519/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding Foreign Key Relationships in EF Core

When working with Entity Framework Core (EF Core), especially in a database-first application, you may encounter issues when your model names do not match your SQL table names. A common scenario arises when you try to define a one-to-many relationship between models, only to run into errors such as:

[[See Video to Reveal this Text or Code Snippet]]

The Problem

You may have definitions similar to the following:

[[See Video to Reveal this Text or Code Snippet]]

And you may have configured your OnModelCreating method like this:

[[See Video to Reveal this Text or Code Snippet]]

The Root Cause

The root cause of the error is that EF Core is trying to infer foreign key names based on conventions. Since there's no foreign key defined in your Book class that connects it to the Author class (like AuthorId), EF is searching for a column with the default naming convention (AuthorAuthorId) that doesn't exist in your table.

The Solution

To resolve this issue, you need to do two things:

Add a Foreign Key Property to Your Model

Configure the Relationship in OnModelCreating Method

Step 1: Add a Foreign Key Property

Modify your Book class to include a foreign key property that references the AuthorId:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Configure the Relationship

Next, in the OnModelCreating method of your DbContext, configure the relationship using the HasOne() and WithMany() methods, and specify the foreign key explicitly:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By defining the AuthorId foreign key property in the Book model and configuring the relationship properly using the Fluent API, you can resolve errors related to foreign key constraints in EF Core. This ensures that your application can properly navigate from the Book model to the Author model, regardless of the actual table names in your database.

If you ever find yourself in a similar situation, remember to check your model definitions and their relationships to avoid these common pitfalls in EF Core applications.

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