How can I transform an SQL query into an EF LINQ query?

Data and Databases
1

I’m in the process of converting a SQL query that involves two table joins to an Entity Framework LINQ query within a .NET 6 application. The SQL query involves joining two tables based on the following condition:

substring(a.someText, 0, len(a.someText) - (len(a.someText) - charindex('_', a.someText) + 1))

I’ve attempted to translate this into EF LINQ as shown below, but I’m encountering an error indicating that it cannot translate IndexOf to SQL:

someText.Substring(0, someText.Length - (someText.IndexOf('_') + 1))

Error Message:

Additional information: Translation of method ‘string.IndexOf’ failed

2

Hey Alex! Have you tried using AsEnumerable or ToList after selecting the needed data to execute the IndexOf operation in memory instead of server-side? Also, maybe consider splitting the string operations to make it more manageable before translation. That sometimes helps in avoiding translation errors with complex logic.

3

You can also consider using a raw SQL query feature in Entity Framework for this particular situation. While it’s generally advisable to stick with LINQ for maintainability and readability, using SqlQuery or FromSqlRaw can sometimes bypass complex translation issues. By using these methods, you can execute the SQL statement directly against the database, which would allow your substring and index logic to remain unchanged and operate as expected without encountering translation errors.

4

Have you thought about checking if the logic can be rewritten in a way that takes advantage of EF’s native methods? Sometimes rethinking how joins and conditions are structured can work wonders. What specific outcome are you aiming for in terms of data manipulation? That might open new ways to approach this.