Resolving the SqlException: How to Avoid Duplicate Key Errors in Your WPF Application

Описание: Struggling with a `SqlException` in your WPF application? Learn how to resolve the issue of duplicate keys when adding records to your database with these easy steps.
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This video is based on the question https://stackoverflow.com/q/64516730/ asked by the user 'Termesz' ( https://stackoverflow.com/u/14513244/ ) and on the answer https://stackoverflow.com/a/64550990/ provided by the user 'Termesz' ( https://stackoverflow.com/u/14513244/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Resolving the SqlException: How to Avoid Duplicate Key Errors in Your WPF Application

If you're a developer working in WPF (Windows Presentation Foundation) and using Entity Framework, you might encounter a frustrating issue: the SqlException: Violation of PRIMARY KEY constraint error. This error occurs when you're trying to insert a duplicate key into a table, as reported in the case of a WPF application named "ContactManager." In this guide, we will explore how to solve this issue and ensure your application runs smoothly.

Understanding the Problem

In the provided scenario, the user faced an exception when attempting to add a new contact to the database after restarting the application. The error message indicated a violation of the primary key constraint, specifying that the application was trying to insert an already existing key (in this case, the value 1). This issue raised concerns about why the system was not generating new unique keys as expected.

Key Pieces of Code

The problem originates from the way the database context is managed and how records are retrieved:

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

In this method, the application retrieves existing contacts but does not manage the database context lifecycle properly.

The Solution

Upon close investigation, it was determined that after calling GetAll(), the database context needed to be disposed of to avoid retaining the previous state, which includes any existing records and their corresponding primary keys.

Step-by-step Solution

Dispose of the Current Context: After retrieving the existing contacts from the database, you should immediately dispose of the current context to ensure that stale data does not interfere with new entries.

Update your ContactRepository constructor as follows:

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

Implementing Changes in the Add Method: Ensure that your Add method resets the context after saving changes. This is crucial for subsequent operations.

For example:

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

Consider Alternative Ways to Manage Context: Continuous disposal may seem like a workaround. For better management, consider implementing a disposable repository pattern where the context is instantiated once and reused across operations without unnecessary disposals.

Moving Forward

After implementing these changes, the application should now add records without triggering the duplicate key error. This ensures that your WPF application can gracefully handle database entries and maintain data integrity.

Final Thoughts

Understanding how Entity Framework manages context and records is crucial for developing robust applications. By ensuring your database context is correctly disposed of and recreated as necessary, you can avoid common pitfalls like duplicate key errors.

Feel free to share your experiences or any additional tips regarding WPF and Entity Framework in the comments below!