using System;

using System.Globalization;

public class Program

{

    public static void Main()

    {   

        // returns -1 in NET45 , but returns 1 in NET5.0. This is breaking change, but why?

        Console.WriteLine(string.Compare(".", "_", StringComparison.InvariantCulture));

        Console.WriteLine(string.Compare(".", "_", StringComparison.CurrentCulture));       

        var cultureInfo = new CultureInfo("en-US", false);

        Console.WriteLine(string.Compare(".", "_", true, cultureInfo));             

        Console.WriteLine(string.Compare(".", "_", StringComparison.Ordinal));              

    }

}