判断是否为中文

判断是否为中文
    public string IsChina(string CString)
    {
        string ResultValue = string.Empty;
        for (int i = 0; i < CString.Length; i++)
        {
            if (Convert.ToInt32(Convert.ToChar(CString.Substring(i, 1))) < Convert.ToInt32(Convert.ToChar(128)))
            {
               
            }
            else
            {
                ResultValue += CString.Substring(i,1);
            }
        }
        return ResultValue;
    }