Efficiently Querying with EF Core 7 and AutoMapper: Handling Multiple Navigations

Explore how to make your `EF Core 7` queries efficient while using `AutoMapper` with complex navigation properties for your ASP.NET Core Web API.
---
This video is based on the question https://stackoverflow.com/q/76796012/ asked by the user 'Kana Ki' ( https://stackoverflow.com/u/2276468/ ) and on the answer https://stackoverflow.com/a/76799615/ provided by the user 'Steve Py' ( https://stackoverflow.com/u/423497/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How do I make EF Core 7 query with multiple navigations/levels efficient with AutoMapping to Dto?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/licensing
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/by-sa/4.0/ ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Efficiently Querying with EF Core 7 and AutoMapper: Handling Multiple Navigations

When developing ASP.NET Core applications using EF Core 7, you may encounter issues related to querying data, especially when dealing with complex relationships across multiple navigation properties. This scenario can become particularly challenging when you also want to map your entities to Data Transfer Objects (DTOs) using AutoMapper. In this post, we’ll look at how to efficiently query data while avoiding performance pitfalls that commonly arise in these situations.

Understanding the Problem

In many cases, developers might notice that querying a table of Venues becomes extremely slow when using lazy loading, particularly when the query is complex and involves various navigation properties. This slowdown is typically attributable to multiple nav queries being executed as AutoMapper attempts to access nested properties within each Venue entity.

To better understand this, let’s break down the process you want to accomplish:

Querying the Data: You want to retrieve data from the Venues table.

Using AutoMapper: The retrieved data should be mapped to a DTO for API responses.

Returning Data Efficiently: Finally, the mapped data should be returned through your API endpoint.

The issue arises when LazyLoadingProxies are used, leading to individual database calls for each navigation property, which can drastically affect performance.

The Solution: Optimizing Queries with Eager Loading

To remedy this and ensure efficient data retrieval, the following recommendations can help:

1. Leverage Eager Loading

When using AutoMapper, by defining which navigation properties to load concurrently with the primary entity, you can significantly improve performance. Instead of relying on lazy loading, consider employing eager loading strategies.

Using Include and ThenInclude:

[[See Video to Reveal this Text or Code Snippet]]

2. Avoiding AsEnumerable() Where Possible

Utilizing AsEnumerable() converts your query into an in-memory collection, losing the benefits of IQueryable. Try to keep the query within SQL context for as long as possible.

Instead of this:

[[See Video to Reveal this Text or Code Snippet]]

Do this:

[[See Video to Reveal this Text or Code Snippet]]

This change will allow the SQL server to handle filtering, making the query faster and more efficient.

3. Use AutoMapper.ProjectTo

To improve how AutoMapper handles mapping expressions, use the ProjectTo feature which translates your mapping to SQL directly from the base query:

[[See Video to Reveal this Text or Code Snippet]]

This method allows for efficient extraction and conversion of your data into DTOs directly at the database level, bypassing the need for individual object access.

4. Implement Split Queries

In situations where you find yourself fetching multiple related entities, applying AsSplitQuery() can further speed up the process by splitting queries rather than running large Cartesian product joins:

[[See Video to Reveal this Text or Code Snippet]]

5. Maintainability for Future Development

In order to keep your query configurations simple and maintainable, you should encapsulate your query logic within methods or services. This makes it easier to keep track of your eager-loading configurations. Whenever a new navigation property is added, it can be easily managed within these methods.

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By utilizing the strategies outlined above, you can significantly enhance the performance of your EF Core 7 queries, especially when using complex navigation properties with AutoMapper. Eager loading, avoiding unnecessary in-memory operatio

Видео Efficiently Querying with EF Core 7 and AutoMapper: Handling Multiple Navigations канала vlogize