Resolving the PRIMARY KEY constraint Violation in Entity Framework Core

Описание: Encountering a `PRIMARY KEY constraint` violation while creating matches in Entity Framework Core? Learn how to resolve this issue with step-by-step guidance.
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This video is based on the question https://stackoverflow.com/q/74661920/ asked by the user 'UntitledUserForEach' ( https://stackoverflow.com/u/17775991/ ) and on the answer https://stackoverflow.com/a/74662456/ provided by the user 'محمد النعيمي' ( https://stackoverflow.com/u/2925326/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving the PRIMARY KEY constraint Violation in Entity Framework Core

Developing applications using Entity Framework Core can sometimes lead to unexpected challenges. One common issue developers encounter is the PRIMARY KEY constraint violation. This error can occur when you attempt to insert a duplicate key into a table in the database, leading to the upset of data integrity. In this guide, we will walk through a specific scenario involving users and matches, explaining why this error occurs and how to resolve it effectively.

The Problem: Duplicate Key Insertion

Imagine that you are trying to create a match between two users in your application. However, you come across an error message that reads:

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Why is this Happening?

This error typically arises when the system identifies two entries with the exact same key when attempting to save changes to the database. In your case, both User instances involved in creating a Match are being treated as new objects. When these instances are saved, their identifiers might clash with existing entries in the database, causing the application to throw a DbUpdateException.

The Solution: Update Match Creation Logic

To resolve this issue, instead of adding complete User objects to the Match, you should only store their identifiers (IDs). This modification ensures you are linking the Match to existing users without causing conflicts. Here’s how you can implement this solution step-by-step.

Step 1: Update the Match Class

Modify your Match class to include the properties for the user IDs:

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Step 2: Adjust the Match Creation Logic

Next, update the Handle method in your command handler to set the user IDs instead of the user objects:

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Step 3: Update the CreateAsync Method

Make sure your CreateAsync method in the MatchRepository is properly handling the newly structured Match object:

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

Conclusion

In summary, encountering a PRIMARY KEY constraint violation in Entity Framework Core can often be traced back to attempting to save duplicate user entries. By adjusting the way you handle relationships in your match model—specifically by utilizing user IDs instead of user objects—you can effectively resolve this issue. This approach reduces redundancy and ensures the integrity of your database entries.

If you face similar challenges while working with Entity Framework Core, remember to check how you manage relationships and object states within your database context. Happy coding!