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Learn how to prevent unintentional updates to CreatedOn and CreatedBy fields in EF Core with effective strategies and best practices.
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Understanding DbContext.SaveChanges Overrides in EF Core: Avoiding Unwanted Updates

When working with Entity Framework Core (EF Core) in a .NET 5 application, you might encounter unexpected behaviors when overriding the DbContext.SaveChanges method. A common issue arises when the CreatedOn and CreatedBy fields are updated unintentionally during an update operation instead of remaining unchanged. In this guide, we'll explore the problem in detail and provide a clear solution that will help you maintain the integrity of your data.

The Problem

In a typical EF Core setup, a model may inherit from a base class that automatically manages properties like CreatedOn, CreatedBy, UpdatedOn, and UpdatedBy. The goal is to ensure that these properties are set correctly on inserts and should remain unchanged on updates.

However, developers have reported issues where the CreatedOn and CreatedBy fields are being updated during entity modifications, leading to unwanted data overwrites. Here's a brief overview of the related code:

The Base Model

The base class for your models may look like this:

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

The SaveChangesAsync Method

The method that overrides SaveChangesAsync to set the created and updated properties might look as follows:

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

When adding or modifying an entity, all of the properties are being updated instead of just the UpdatedOn and UpdatedBy fields.

The Solution

Thanks to a suggestion from the community, there's an effective way to fix this issue. By explicitly marking CreatedOn and CreatedBy as not modified during an update, you can prevent these fields from being overwritten by default values.

Here's how to implement this solution in your SaveChangesAsync method:

Step-by-Step Implementation

Modify the SaveChangesAsync method to include the following check for properties:

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

Additionally, remove the ValueGenerated* properties from your configuration, as these can interfere with manual property management.

Finally, ensure that you also remove the [DatabaseGenerated(DatabaseGeneratedOption.Identity)] attributes from your base model.

Updated SaveChangesAsync Method

Here’s the updated method with these changes applied:

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

Conclusion

By implementing the above modifications to your SaveChangesAsync method, you should now be able to effectively control when the CreatedOn and CreatedBy fields are set, ensuring they are only modified during insert operations. This not only keeps your data consistent but also preserves the integrity of your application.

If you have similar issues or further questions, feel free to reach out or comment below. Happy coding!