False positive in csharp for useless-assignment-to-local

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#22,032 opened on Jun 22, 2026 1 comment 0 reactions 1 assignee View on GitHub

@hvitved is already working on this.

Since Jun 23, 2026.

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Description

false-positive

Description of the false positive

The context is the following: the variable is used inside a lambda and captured by it.

It is not clear to me what the exact cause is. I tried to create a self-contained code sample, but I was not able to trigger the false positive that way, so the sample code relies on AspNetCore, which is the context where I got the warning.

Code samples or links to source code

To reproduce, you need a project that depends on AspNetCore, which is possible with a project file like the following: Sample.csproj:

<Project Sdk="Microsoft.NET.Sdk.Web">
</Project>

The following is helper code to configure a AspNetCore WebApplication:

public static class App
{
    extension(WebApplication app)
    {
        public void Configure()
        {
            string redirectPath = "/app";
            app.MapGet("/", () => Results.Redirect(redirectPath));
        }
    }
}

CodeQL complains about the redirectPath not being used. The type of the lambda passed to MapGet is Delegate. An example with self-contained code with a similar setup and the use of a Delegate type did not trigger the false positive.

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False positive in csharp for useless-assignment-to-local

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