Gergő Vándor delves into Entity Framework Core’s global query filters, explaining their functionality, usage, and practical scenarios to consider.

Overview

In this article, Gergő Vándor examines the concept of global query filters in Entity Framework Core (EF Core). The discussion is aimed at developers seeking efficient ways to manage common filtering logic at the model level within their applications.

What Are Global Query Filters?

Global query filters in Entity Framework Core allow developers to define filters that are automatically applied to all queries involving a particular entity type. These filters are typically defined in the OnModelCreating method of your application’s DbContext, making them reusable and consistent across the application. Common use cases include soft deletes, multi-tenancy, and enforcing application-wide security policies.

How to Use Global Query Filters

  • Definition: Global query filters are LINQ predicate expressions attached to entity types. For example, a filter could hide ‘soft-deleted’ records by excluding entities where an IsDeleted flag is true.

  • Implementation: Global filters are written in the OnModelCreating method using the HasQueryFilter method on the ModelBuilder entity configuration:

    modelBuilder.Entity<MyEntity>().HasQueryFilter(e => !e.IsDeleted);
  • Multiple Entities: You can define global filters for multiple entities, making it easy to enforce consistency without redundant logic in every query.

Scenarios and Considerations

  • Combining Filters: When composing LINQ queries, global filters apply automatically but can be combined with additional query-level filters as necessary.
  • Disabling Filters: In scenarios where you need to override or bypass the filter (for example, in admin views), you can disable global filters using the IgnoreQueryFilters method.
  • Caveats: Developers should be aware that global query filters apply to navigational properties as well, which may lead to unexpected results if not considered during design.

Practical Tips

  • Use global query filters for repeated or mandatory filtering logic, such as soft deletes, tenant isolation, or access controls.
  • Document where and why filters are applied to avoid confusion in complex data models.
  • Test thoroughly, especially when working with related entities or eager loading, as filters may impact the data returned.

Conclusion

Global query filters in EF Core are a powerful tool for simplifying and centralizing common query logic. However, developers must understand their application and side effects to leverage them effectively in real-world scenarios.

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