Fixing .NET MVC Entity Framework SaveChanges Not Working

Learn how to troubleshoot and fix issues with the SaveChanges method in .NET MVC using Entity Framework in this detailed guide.
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This video is based on the question https://stackoverflow.com/q/68078055/ asked by the user 'Kamran Teymurov' ( https://stackoverflow.com/u/9234798/ ) and on the answer https://stackoverflow.com/a/68078203/ provided by the user 'Nagaraj Raveendran' ( https://stackoverflow.com/u/5402254/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem with SaveChanges in .NET MVC Entity Framework

If you’ve been working with .NET MVC and the Entity Framework, you may have encountered a frustrating issue: the SaveChanges() method doesn't seem to work, even though it executes without throwing any errors. In this guide, we will explore a common scenario that leads to this problem and provide a clear solution. Let’s dive in!

The Scenario

Imagine you have a simple update operation where you want to update an entity in your database. Here's what your original code might look like:

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

Despite the logical flow, you're not seeing the changes reflected in your database. This can be quite perplexing, especially for those new to the Entity Framework.

The Core Issue

The main problem arises from the line where the record is being fetched. In your code, you're using db.WFileMaster which suggests that you are referencing a different database context rather than the one you just created (context).

Incorrect Context: By fetching data using a different context, any modifications made to the retrieved entity do not track back to the context, and thus, the SaveChanges() call doesn't know what to save.

The Solution

To resolve this issue, you simply need to ensure that you are consistently using the same context throughout your operation. Here’s how you can modify your code:

Updated Code

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

Key Changes Made

Use of Context: The key change is in the second line where we now use context.WFileMaster instead of db.WFileMaster. This ensures any changes made are properly tracked by the same context instance.

Null Check: Added a check to ensure that query is not null before proceeding to update the properties. This prevents potential NullReferenceExceptions if the ID does not match any record.

Conclusion

With these simple adjustments, your SaveChanges() method will now work as expected, applying updates to your database effectively. If you’re encountering similar problems, always remember to check that you are working with the correct context and you're directly interacting with the entities being managed by that context.

By following this guide, you should now feel more comfortable troubleshooting and resolving common issues in the Entity Framework. Happy coding!

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