string s1 = "abcd博客园cnblogs";
            string s2 = "Visual Studio 2005和Visual Studio 2008那个好";

            string result = string.Empty, result1 = string.Empty;
            Regex regex = new Regex(@"[a-zA-Z0-9]*", RegexOptions.Multiline | RegexOptions.IgnoreCase);
            MatchCollection mc = regex.Matches(s1);
            foreach (Match match in mc)
                if (match.Success)
                    result += match.Value;
            MatchCollection mc1 = regex.Matches(s2);
            foreach (Match match in mc1)
                if (match.Success)
                    result1 +=" "+ match.Value;

 public static void Main(string[] args)
        {
            string oldstr = "abcd博客园cnblogs,visual studio 2005和visual studion 2008的区别";
            Console.WriteLine(FilterChIneseChar(oldstr));
            Console.ReadKey();
        }
        private static string FilterChIneseChar(string oldstring)
        {
            if (string.IsNullOrEmpty(oldstring))
            {
                return string.Empty;
            }

            ////if (!IsChinese(oldstring))
            ////{
            ////    return oldstring;
            ////}
            System.Text.StringBuilder result = new System.Text.StringBuilder();

            for (int i = 0; i < oldstring.Length; i++)
            {
                char ch = oldstring[i];
                if (!IsChinese(ch))
                {
                    result.Append(ch.ToString());
                }
            }
            return result.ToString();
        }
        #region    RegularExpression

        public static bool IsChinese(string text)
        {
            return System.Text.RegularExpressions.Regex.Match(text, ConstChineseRegex, System.Text.RegularExpressions.RegexOptions.Compiled).Success;
        }
        public static bool IsChinese(char ch)
        {
            return IsChinese(Convert.ToString(ch));
        }
        public const string ConstChineseRegex = @"^[\u4e00-\u9fa5]+$";
        #endregion