Explicit Loading in EF Core

Explicit loading lets you load related data on demand, after the main entity has already been retrieved. In EF Core, explicit loading starts from DbContext.Entry(...).

If you already know the related data is needed with the initial query, see Eager Loading in EF Core. Explicit loading is useful when that decision should happen later.

Load a Reference Navigation Explicitly

Use Reference(...) when the navigation points to a single related entity.

var blog = await context.Blogs
    .SingleAsync(blog => blog.BlogId == 1);

await context.Entry(blog)
    .Reference(blog => blog.Owner)
    .LoadAsync();

Console.WriteLine(blog.Owner?.Name);

The first query retrieves the Blog without explicitly requesting its Owner navigation.

context.Entry(blog) accesses the EF Core entry for the loaded Blog. Reference(blog => blog.Owner) selects the Owner navigation, and LoadAsync() loads the related entity from the database.

Once the load completes, the related entity is available through blog.Owner.

Calling Entry(...) and Reference(...) only identifies the entity and navigation to work with. The related data is not explicitly loaded until LoadAsync() is called.

This is different from Eager Loading in EF Core, where related data is requested as part of the initial query. Explicit loading lets the application decide later whether and when the navigation should be loaded.

For navigations that contain multiple related entities, use Collection(...) instead.

Load a Collection Navigation Explicitly

Use Collection(...) when the navigation contains multiple related entities.

var blog = await context.Blogs
    .SingleAsync(blog => blog.BlogId == 1);

await context.Entry(blog)
    .Collection(blog => blog.Posts)
    .LoadAsync();

foreach (var post in blog.Posts)
{
    Console.WriteLine(post.Title);
}

The first query retrieves the Blog without explicitly requesting its Posts navigation.

Collection(blog => blog.Posts) selects the collection navigation, and LoadAsync() loads the related Post entities. After the operation completes, the posts are available through blog.Posts.

The distinction between the two APIs is the shape of the navigation:

• Reference(...) targets a single related entity, such as blog.Owner.
• Collection(...) targets multiple related entities, such as blog.Posts.

Both follow the same explicit-loading pattern:

await context.Entry(entity)
    .Reference(...)
    .LoadAsync();

await context.Entry(entity)
    .Collection(...)
    .LoadAsync();

If you do not need the entire collection—for example, if you only need a count or a filtered subset—you can access the navigation as a query with Query().

Query a Navigation with Query()

Query() exposes the query that represents a navigation, allowing you to compose LINQ operators before executing it.

Get Information Without Loading the Entire Collection

For example, you can count the related posts without loading them into memory:

var blog = await context.Blogs
    .SingleAsync(blog => blog.BlogId == 1);

var postCount = await context.Entry(blog)
    .Collection(blog => blog.Posts)
    .Query()
    .CountAsync();

Console.WriteLine(postCount);

Collection(blog => blog.Posts) identifies the Posts navigation, while Query() exposes it as a LINQ query.

CountAsync() executes an aggregate query and returns the number of related posts as an int. The application gets the count without materializing the Posts collection.

Filter Related Entities

You can also compose the navigation query before materializing matching entities.

var blog = await context.Blogs
    .SingleAsync(blog => blog.BlogId == 1);

var goodPosts = await context.Entry(blog)
    .Collection(blog => blog.Posts)
    .Query()
    .Where(post => post.Rating > 3)
    .ToListAsync();

foreach (var post in goodPosts)
{
    Console.WriteLine(post.Title);
}

Here, Query() exposes the related Posts as a query, Where(...) filters it, and ToListAsync() executes the query and returns a List<Post> containing only the matching entities.

In a tracking query, those Post entities can also be added to blog.Posts through relationship fixup. However, querying only part of the collection with Query() does not mark the navigation as fully loaded.

Query() itself does not execute the database query. It returns an IQueryable that can be composed with LINQ operators. Execution happens when a terminal operation such as CountAsync() or ToListAsync() is called.

Use Query() when you need to query a navigation rather than load all of its related entities with LoadAsync().

Load Related Entities Through the Change Tracker

Related entities can also become connected through EF Core's Change Tracker when they are loaded by a separate query.

var blog = await context.Blogs
    .SingleAsync(blog => blog.BlogId == 1);

var posts = await context.Posts
    .Where(post => post.BlogId == blog.BlogId)
    .ToListAsync();

The first query loads the Blog. The second query separately materializes its related Post entities.

When change tracking is enabled, EF Core recognizes relationships between newly materialized entities and entities that are already being tracked. It then performs relationship fixup by updating the relevant navigation properties.

In this example, EF Core connects the newly loaded Post entities to the already tracked Blog.

This is different from calling Collection(...).LoadAsync() or Reference(...).LoadAsync(). Those APIs explicitly target a navigation to load. Here, the application runs a separate query, and the Change Tracker connects the related tracked entities.

For a deeper explanation of tracking behavior, see Query Tracking in EF Core.

Explicit Loading vs. Eager Loading vs. Lazy Loading

EF Core supports different strategies for loading related data. The main difference is when the related data is loaded.

Use Eager Loading in EF Core when you already know the related data is needed with the main query.

Use explicit loading when related data should be retrieved later, under application control.

Lazy loading follows a different model because EF Core loads related data automatically when a navigation is accessed. See Lazy Loading in EF Core for that behavior.

When Should You Use Explicit Loading?

Use explicit loading when you already have the main entity and whether related data is needed depends on what happens next.

Typical cases include:

• loading a navigation only when a condition is met;
• retrieving only specific navigations after the main entity has already been loaded;
• querying a relationship with Query() instead of loading the entire navigation.

Because explicit loading can execute additional database queries, avoid repeatedly loading navigations without considering how many queries the application will generate.

External Resources - Explicit Loading

The following videos complement the examples in this article with practical demonstrations of explicit loading in EF Core. Together, they cover collection and reference navigations, conditional and nested loading with LoadAsync(), relationship fixup through the Change Tracker, and navigation queries built with Query().

Video 1 - Eager, Lazy and Explicit Loading in Entity Framework Core

DotNetMastery demonstrates explicit loading with both collection and reference navigations using DbContext.Entry(...), Collection(...), Reference(...), and Load(). The debugger and EF Core logs make it possible to see when related data is not initially populated and when an additional database query is executed to load it.

The video also shows a useful Change Tracker behavior: a VillaAmenity.Villa reference is already populated because the related Villa was previously loaded in the same DbContext. Although the presenter does not use the formal term relationship fixup, the demonstration provides a clear visual example of that behavior.

The timestamps below focus on the Explicit Loading segments that remain directly relevant to current EF Core usage.

Key timestamps:

• 19:08 — Introduces explicit loading and explains that related data can be loaded later as either a collection or a reference navigation.
• 20:27 — Builds the collection example with Entry(...).Collection(...).Load() to load VillaAmenity for a single Villa.
• 21:50 — Introduces explicit loading for a reference navigation and explains why Reference(...) is used instead of Collection(...).
• 23:06 — Shows the related Villa already populated because it was previously loaded in the same DbContext, providing a practical illustration of relationship fixup.

Video 2 - Eager, Explicit & Lazy Loading in EF Core

Remigiusz Zalewski demonstrates explicit loading with the asynchronous LoadAsync() API in a practical e-commerce scenario. Instead of loading every relationship up front, the example applies business rules to decide which customers, orders, items, and products should have related data loaded.

It shows Collection(...).LoadAsync() for collection navigations and Reference(...).LoadAsync() for a single related entity, then executes the flow while displaying the additional SQL statements generated by those explicit loads.

Key timestamps:

• 11:35 — Introduces the business rule that determines which customers should have related data loaded explicitly instead of loading every relationship up front.
• 12:34 — Uses Entry(customer).Collection(...).LoadAsync() to load the customer's Orders collection asynchronously.
• 14:29 — Uses Entry(item).Reference(...).LoadAsync() to load a related Product only when the item's quantity satisfies the configured condition.
• 15:40 — Executes the explicit-loading flow and shows the additional SQL statements produced according to the business rules.

This resource adds useful depth by showing how explicit loading can be applied asynchronously and selectively across multiple levels of a related entity graph.

Video 3 - ASP.NET Web API + Entity Framework Core: Loading Related Data | Explicit Loading - EP06

CuriousDrive demonstrates how Query() can be used to compose a query over a navigation before execution. This complements the previous resources, which focus primarily on Load() and LoadAsync().

The useful segments show two practical navigation-query patterns: adding Include(...) to load another related level and applying Where(...) to filter which related entities are loaded. Because the video predates filtered Include, the timestamps below focus specifically on its still-useful Query() demonstrations.

Key timestamps:

• 5:11 — Uses Collection(...).Query() on the publisher's Books navigation, exposing the related books as a composable query.
• 5:56 — Shows the complete Collection(...).Query().Include(...).Load() pattern to load books together with their related Sales.
• 6:21 — Builds a filtered navigation query with Collection(...).Query().Where(...) to restrict which related users are loaded.
• 6:49 — Shows the filtered result, where the Users navigation contains only the entity matching the configured condition.

This resource adds the Query() dimension to the set and shows how explicit loading can be combined with LINQ composition before related entities are materialized.

Summary

Explicit loading gives you control over when related data is retrieved after the main entity has already been loaded.

• Use Reference(...).LoadAsync() for a single related entity and Collection(...).LoadAsync() for a collection.
• Use Query() to count, filter, or otherwise compose a query over a navigation before execution.
• With change tracking enabled, separately loaded related entities can also be connected through relationship fixup.

Related Articles

Explicit loading is one of several ways EF Core can work with related data. The following articles explain the neighboring querying and loading behaviors in more detail:

• Eager Loading in EF Core — Load related data together with the main entity.
• Lazy Loading in EF Core — Load related data automatically when a navigation is accessed.
• Include in EF Core — Use Include and ThenInclude to specify related data in the original query.
• Query Tracking in EF Core — Understand how tracked and no-tracking queries behave.
• LINQ Queries in EF Core — Learn how EF Core queries are composed and executed.

FAQ

Does explicit loading always load the entire navigation?

No. LoadAsync() loads the targeted navigation, but Query() lets you work with its underlying query instead. You can apply operators such as CountAsync() or Where(...) when you do not need the entire relationship.

Does explicit loading execute another database query?

Calling LoadAsync() for an unloaded navigation normally executes a separate database query after the query that loaded the main entity. Once the navigation is marked as loaded, calling LoadAsync() again does not execute another query.

Does Query() mark a navigation as loaded?

Not necessarily. For example, querying only part of a collection with Query().Where(...) does not mark the collection navigation as fully loaded.

Can entities returned through Query() update the navigation property?

Yes. In tracking queries, related entities materialized through the navigation query can be connected to already tracked entities through relationship fixup.

When should I use explicit loading instead of eager loading?

Use eager loading when you already know the related data is needed with the initial query. Use explicit loading when the main entity has already been retrieved and the application should decide later whether additional related data is needed.

Can the Change Tracker connect related entities loaded by separate queries?

Yes. When change tracking is enabled, EF Core can perform relationship fixup between newly materialized entities and related entities that are already being tracked.