


How to Eagerly Load Related Entities with a Where Clause in Entity Framework?
Feb 01, 2025 pm 01:46 PMEfficiently Loading Related Data with Filtering in Entity Framework
This article addresses the challenge of eagerly loading related entities while applying filtering conditions within Entity Framework. The optimal approach depends on your EF version.
Entity Framework 6 Solution
EF6 relies on eager loading and relationship fixup. However, this fixup mechanism doesn't always function correctly with many-to-many relationships. A workaround involves:
-
Disabling Lazy Loading: Prevent lazy loading to ensure all data is retrieved in a single query:
Context.Configuration.LazyLoadingEnabled = false;
-
Projection with Filtering: Use a projection to filter related entities during the query:
var buses = Context.Busses .Where(b => b.IsDriving) .Select(x => new { b, Passengers = x.Passengers.Where(p => p.Awake) }) .AsEnumerable() .Select(x => x.b) .ToList();
-
Automatic Relationship Fixup: EF will automatically populate the
Passengers
property of eachBus
object with only the awake passengers. -
Data Transfer Objects (DTOs): Use a mapping tool like AutoMapper to convert the retrieved data into DTOs for optimal data transfer.
Entity Framework Core (5.0 and later) Solution
EF Core 5.0 and later versions directly support nested includes with where clauses, simplifying the process:
var buses = Context.Busses .Include(bus => bus.Passengers.Where(p => p.Awake)) .ToList();
Alternative Approach: Third-Party Libraries
Libraries like EntityFramework.DynamicFilters
offer a more streamlined method for managing global filters applicable to included collections. This can enhance code readability and maintainability for complex scenarios.
Summary
The best approach for eagerly loading related data with filtering in Entity Framework hinges on the version being used. EF Core 5.0 offers a straightforward solution. For EF6, a workaround involving disabling lazy loading and using projections is necessary. Third-party libraries provide an alternative for improved code organization and flexibility.
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