删除字符串中的中文

var str = "123牛4逼5了";
            string retValue = str;
            if (System.Text.RegularExpressions.Regex.IsMatch(str, @"[\u4e00-\u9fa5]"))
            {
                retValue = string.Empty;
                var strsStrings = str.ToCharArray();
                for (int index = 0; index < strsStrings.Length; index++)
                {
                    if (strsStrings[index] >= 0x4e00 && strsStrings[index] <= 0x9fa5)
                    {
                        continue;
                    }
                    retValue += strsStrings[index];
                }
            }
          return  retValue;