This is not at all just an LLM thing. I've been working with C# and MS SQL Server for many years and never even considered this could be happening when I use Dapper. There's likely code I have deployed running suboptimally because of this.

And it's not like I don't care about performance. If I see a small query taking more than a fraction of a second when testing in SSMS or If I see a larger query taking more than a few seconds I will dig into the query plan and try to make changes to improve it. For code that I took from testing in SSMS and moved into a Dapper query, I wouldn't have noticed performance issues from that move if the slowdown was never particularly large.

This is a common issue, and most developers I worked with are not aware of it until they see the performance issues.

Most people are not aware of how Dapper maps types under the hood; once you know, you start being careful about it.

Nothing to do with LLMs, just plain old learning through mistakes.

actually, LLMs do way better, with dapper the LLM generates code to specify types for strings