Serenity.Q.TrimToNull C# (CSharp) Method

        public static string TrimToNull(this string str)
        {
            if (str == null || str.Length == 0)
                return null;
            else
            {
                str = str.Trim();
                if (str.Length == 0)
                    return null;
                else
                    return str;
            }
        }