Convert string into Title Case in C#

Convert string into Title Case in C#  by Extension method

1.      using TextInfo class. 

public static class StringExtension

    {

        /// <summary>

        /// Use to convert string into Title Case

        /// </summary>

        /// <param name="str"></param>

        /// <returns></returns>

        public static string ToTitleCase(this string str)

        {

            if (!String.IsNullOrEmpty(str))

                return System.Threading.Thread.CurrentThread.CurrentCulture.TextInfo.ToTitleCase(str.ToLower());

            return null;

        }

    }

    class Program

    {

        static void Main(string[] args)

        {

            string str = "convert STRING into titlecase in c#"; 

            Console.WriteLine( str.ToTitleCase());

            Console.ReadLine();

        }

    }