[SimpleJob]
[MeanColumn, MinColumn, MaxColumn]
[MemoryDiagnoser]
public class Bench
{
    [Params(null, "")] // or null, 1
    public string? Value { get; set; } // or int?

    [Benchmark]
    public bool Method()
    {
        bool result = false;
        for (int i = 0; i < 10; i++)
        {
            result = Value is null; // change every benchmark case
        }
        return result;
    }
}

[SimpleJob]
[MeanColumn, MinColumn, MaxColumn]
[MemoryDiagnoser]
public class EqualityComparerBench
{
    [Benchmark]
    public IEqualityComparer<string?> StringEqualityComparer()
    {
        return EqualityComparer<string?>.Default;
    }

    [Benchmark]
    public IEqualityComparer<int?> IntEqualityComparer()
    {
        return EqualityComparer<int?>.Default;
    }
}