public static bool IsChineseCh(string input)
        {
            Regex regex = new Regex("^[\u4e00-\u9fa5]+$");
            return regex.IsMatch(input);
        }if (IsChineseCh(""))
                    {
                      MessageBox .Show("YES");
                    }
                    else
                    {
                        MessageBox.Show("NO"); 
                    }