string str = "aaaaaaaaaaa123bbb#@$";
            double count = Regex.Replace(str, @"[^a-zA-Z\u4e00-\u9fa5]", "").Length;
            Console.WriteLine(Math.Round(count / 10));

------解决方案--------------------
string s = "I Love 中文字";
               int count=0;
               foreach (char c in s)
               {
                   if ((short)c > 256)
                       count++;
               }
               Console.WriteLine((count/10.0).ToString("f0"));

------解决方案--------------------
C# code
string s = "I Love 中文字";
                int count=0;
                foreach (char c in s)
                {
                    if ((short)c > 256)
                        count++;
                }
                Console.WriteLine((count/10.0).ToString("f0"));