Resolving Issues with Entity Framework Core Contains for Accurate Data Selection
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Discover how to troubleshoot and enhance your `Entity Framework Core` queries to retrieve accurate data using `EF.Functions.Like` instead of `Contains`.
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This video is based on the question https://stackoverflow.com/q/77536035/ asked by the user 'Ja Da' ( https://stackoverflow.com/u/13898633/ ) and on the answer https://stackoverflow.com/a/77536171/ provided by the user 'Ja Da' ( https://stackoverflow.com/u/13898633/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.
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Troubleshooting Data Selection in Entity Framework Core
When working with Entity Framework Core, developers often face various challenges while trying to query data accurately. One common issue arises when trying to use the Contains method for complex SQL-like queries. In this post, we delve into a specific scenario where a developer faced unexpected results when applying Contains and how switching to EF.Functions.Like can remedy this.
The Problem: Inaccurate Count Results
Imagine you are querying a database using Entity Framework Core in a .NET 6 application. You have two subqueries that you expect to return a total count of relevant records. However, after rewriting an SQL query in LINQ, you find that the results are lower than anticipated.
The Original SQL Query
The original SQL statement successfully retrieved counts based on specific conditions:
[[See Video to Reveal this Text or Code Snippet]]
The LINQ Version
After converting this to LINQ, the two queries are structured as follows:
[[See Video to Reveal this Text or Code Snippet]]
However, the results you get are inconsistent, yielding 3 results instead of the expected 5.
The Solution: Using EF.Functions.Like
After analyzing generated SQL queries, it was identified that the issue lay with the Contains method not properly translating to the SQL LIKE functionality for the required pattern matching.
The Correct Approach
To resolve this, you can leverage EF.Functions.Like, which directly correlates with SQL's LIKE operator, thus better serving the querying needs in a more expected manner.
Here’s how to modify the LINQ queries:
[[See Video to Reveal this Text or Code Snippet]]
Benefits of Using EF.Functions.Like
Accurate Pattern Matching: EF.Functions.Like provides SQL-like searching capabilities.
Better Result Consistency: Eliminates discrepancies in result counts when querying based on substring matches.
Easy Transition from Queries: Minimal changes required to migrate existing LINQ queries to utilize the Like functionality.
Conclusion
Switching from Contains to EF.Functions.Like can significantly enhance your ability to retrieve accurate results when querying with conditions that involve substring searches. Always ensure to analyze your queries and their translated SQL forms for unexpected results and consider utilizing available SQL functions for precision.
Improving data selection processes in Entity Framework Core allows for more reliable and accurate applications, ultimately leading to better decision-making based on data insights.
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