Global Query Filters allow you to define LINQ predicates at the model level. Once defined, these predicates automatically get applied to all queries involving that entity — including queries made via navigation properties or explicit LINQ queries.
This approach works, but it's redundant. Every time you query for Products, you need to remember to add the !product.IsDeleted filter. This not only makes your code verbose but also introduces a risk of forgetting the filter, leading to accidentally retrieving soft-deleted data.
How to Apply a Global Query Filter
Implementing a global query filter in EF Core involves these simple steps:
Standard Configuration Pattern: It aligns perfectly with EF Core's existing model configuration practices.
Override OnModelCreating: You begin by overriding the OnModelCreating method within your custom DbContext class. This is where EF Core's Fluent API configurations are typically defined.
Leverage HasQueryFilter: Inside OnModelCreating, you'll use the HasQueryFilter method.
Target Entities: This HasQueryFilter method is applied to the specific entities for which you want to automatically enforce a filter on all queries.
Conclusion
Global Query Filtering in EF Core is a powerful feature that promotes cleaner code, reduces redundancy, and helps enforce data integrity across your application. By automatically applying common filters, especially for patterns like soft deletion, you can significantly improve developer experience and reduce the chances of data-related bugs.
Embrace Global Query Filtering in your EF Core projects and say goodbye to repetitive WHERE clauses!