Contains before Add or Remove on a set (CA1868)
Key dotnet.performance.contains-before-add · Severity info · Category performance
Microsoft analyzer CA1868. Flags Contains before Add or Remove on a set - both already report whether they changed anything.
Incorrect
Section titled “Incorrect”if (!seen.Contains(id)) seen.Add(id);Correct
Section titled “Correct”seen.Add(id); // returns false when it was already there