using System;

using System.Globalization;

public class Program

{

    public static void Main()

    {

    string letra = "i";

        var turkeyCulture = new CultureInfo("tr-TR");

        Console.WriteLine(string.Format("{0} ({1})", letra.ToUpperInvariant(), (int)letra.ToUpperInvariant()[0]));

        Console.WriteLine(string.Format("{0} ({1})", letra.ToUpper(turkeyCulture), (int)letra.ToUpper(turkeyCulture)[0]));

        Console.WriteLine(string.Format("result: ({0})", letra.ToUpper(turkeyCulture) == letra.ToUpperInvariant()));

    }

}