Скачать или смотреть Mastering async Methods in Entity Framework Core: Enhancing Repository Patterns with IEnumerable

Learn how to efficiently implement `async` methods in Entity Framework Core and improve your repository pattern by retrieving specific columns with optimal queries.
---
This video is based on the question https://stackoverflow.com/q/62896322/ asked by the user 'Artavazd' ( https://stackoverflow.com/u/13235902/ ) and on the answer https://stackoverflow.com/a/62896483/ provided by the user 'Johnathan Barclay' ( https://stackoverflow.com/u/8126362/ ) 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: Entity Framework Core IEnumerable async

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

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Mastering async Methods in Entity Framework Core: Enhancing Repository Patterns with IEnumerable

In the realm of C# and ASP.NET Core development, effectively managing data access layers is crucial for building performant applications. The repository pattern is a popular way to structure data interactions, particularly when using Entity Framework Core (EF Core). However, it can often lead to some complex scenarios regarding asynchronous data retrieval.

Recently, a common challenge among developers arose about how to efficiently retrieve a single column from a database table while ensuring the performance of their code remains optimal. This guide will explain how to address this problem based on a specific scenario involving a repository pattern implementation for a Coin entity in EF Core.

The Problem

The challenge presented was about developing a new method called GetValuesAsync within a CoinRepository class. The goal of this method is to retrieve a specific column (Value) based on particular conditions from the Coin table, which includes multiple columns. Here's the initial implementation of the method:

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

This code raises several questions, particularly regarding its efficiency and proper use of asynchronous programming.

Key Concerns

1. Should GetValuesAsync be an async method?

Absolutely! Making GetValuesAsync an async method is essential. When you use .Result, it blocks the thread and undermines the advantage of asynchronous operations—this can lead to performance bottlenecks, especially under load.

2. How does GetAllAsync execute queries?

The GetAllAsync implementation retrieves all records without applying any filters until after the data is loaded into memory. Therefore, it does not leverage SQL efficiently as it would execute a generic query like SELECT * FROM Coin, subsequently filtering with LINQ in C# . This approach can be inefficient.

3. How can we optimize the method performance?

To enhance performance, the method should pass conditions directly to GetAllAsync, allowing EF Core to generate a SQL query that includes these conditions. Here’s how you can refactor the GetValuesAsync method:

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

Why This Refactoring Works

Asynchronous Operations: By marking the method as async, you allow the operation to run without blocking the thread.

SQL Query Optimization: Passing a filter expression to GetAllAsync enables EF Core to construct a more efficient SQL query that fits within the database's processing capabilities.

Selective Column Retrieval: Specifying that you only want the Value column minimizes the amount of data transferred, speeding up response times.

Conclusion

Implementing the repository pattern in EF Core can be initially challenging. However, by leveraging async programming and optimizing your queries, you can significantly enhance application performance and maintainability. The changes suggested here not only ensure better resource management but also align with best practices for developing modern, scalable applications in C# .

As you continue to refine your data access strategies, remember that always questioning and profiling your code can lead to optimizations that provide immediate benefits to performance and user experience.

Feel free to share your experiences or queries on using asynchronous methods within Entity Framework Core!