280 posts tagged with "C#"

I gave a column a case-sensitive collation with EF Core's UseCollation("utf8mb4_0900_as_cs"), created the migration, applied it, and dotnet ef printed Done. The column was still utf8mb4_0900_ai_ci, and MySQL still refused desks as a duplicate of Desks. Oracle's MySQL provider for EF Core leaves UseCollation out of the SQL it generates. Here's how I found that, what Oracle documents instead, and the migration that does change the column.

I built an EF Core migrations bundle, ran it, and got three lines instead of migrations: Failure processing application bundle. Failed to determine location for extracting embedded files. DOTNET_BUNDLE_EXTRACT_BASE_DIR is not set, and a read-write cache directory couldn't be created. The bundle was fine. The folder it extracts into, ~/.net, had belonged to root since 2023.

The migration '20261103044430_MakeDescriptionRequired' has already been applied to the database. Revert it and try again. If the migration has been applied to other databases, consider reverting its changes using a new migration instead. dotnet ef migrations remove checks the database before it deletes anything, and this migration was in it. The message holds both fixes: one for your own development database, one for every other database.

Your target project 'Dewiride.Inventory.Api' doesn't match your migrations assembly 'Dewiride.Inventory.Data'. Either change your target project or change your migrations assembly. dotnet ef built the solution, then refused to write the migration, because it would have put the files in a project where EF Core would never look for them. The message offers two fixes; one of them moves your migrations to the web project, and it's usually not the one you want.

Your startup project 'Dewiride.Inventory.Data' doesn't reference Microsoft.EntityFrameworkCore.Design. This package is required for the Entity Framework Core Tools to work. Ensure your startup project is correct, install the package, and try again. The message offers two fixes, in one sentence. In a solution where the DbContext lives in a class library, the first one is usually right: the tools were using the wrong startup project.

No project was found. Change the current working directory or use the --project option. This is often the first thing dotnet ef prints in a solution with more than one project. It doesn't even build: the folder you're in has no project file for it to use. Here's why, how to see which projects you have, and the command that works.

error CS8618: Non-nullable property 'Description' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable. The compiler is telling you that a property you declared as never-null can be null the moment an object is created. The message names two fixes; there are five, and they mean different things. Here's each one, built for real on an EF Core entity, and how to choose.

Deleting a category through EF Core worked as designed until the request loaded the category's products first. Then the delete failed with System.InvalidOperationException: The association between entity types 'Category' and 'Product' has been severed, but the relationship is either marked as required or is implicitly required because the foreign key is not nullable. It came from Remove(), before any SQL ran, so the error handling around SaveChangesAsync never saw it.

Four different mistakes, one message: Microsoft.EntityFrameworkCore.DbUpdateException: Could not save changes. Please configure your entity type accordingly. A duplicate name, a negative price, a missing category and a blocked delete all produced it, through Oracle's MySQL provider for EF Core. Nothing was wrong with any entity type's configuration. The real reason sits one line lower, in the inner MySqlException, and its error number is what your code should handle.

One row in a table held a name my C# enum didn't have, and every query that read that table failed: System.InvalidOperationException: Cannot convert string value 'Refund' from the database to any value in the mapped 'StockMovementType' enum. Here's why EF Core refuses instead of guessing, how to find every bad value with one query, and how to keep them out.