Code inspection: The parameter expects a constant for optimal performance

This inspection reports arguments passed to parameters annotated with ConstantExpected when the argument is not a compile-time constant. Such APIs are designed to receive values known at compile time. Passing a variable or another non-constant expression usually defeats the purpose of the annotation and can lead to incorrect API usage.

It is the same as the CA1857 code quality rule.

Example

                using System.Diagnostics.CodeAnalysis;
                class C
                {
                    static void Log([ConstantExpected] int eventId) { }
                    void M()
                    {
                        int id = GetEventId();
                        Log(id);
                    }
                }
            

                using System.Diagnostics.CodeAnalysis;
                class C
                {
                    static void Log([ConstantExpected] int eventId) { }
                    void M()
                    {
                        Log(42);
                    }
                }
            

01 April 2026