/// <summary>
/// 邮箱格式验证
/// </summary>
/// <returns></returns>
public static string CheckMail(string strEmail)
{
  string result = "";
  Regex regex = new Regex(@"[a-zA-Z0-9._%-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4}");
  Match match = regex.Match(strEmail);
  if(match.Success)
  {
    result = strEmail;
  }
  else
  {
    result = "无效邮箱";
  }
  return result;
}

/// <summary>
/// 转换日期格式（yyyy-MM-dd 转 yyyy年MM月dd日）
/// </summary>
/// <param name="strDate"></param>
/// <returns></returns>
public static string TransDate(string strDate)
{
  string result = "";
  Regex regex = new Regex(@"(\d+)-(\d+)-(\d+)");
  if(regex.IsMatch(strDate))
  {
    result = regex.Replace(strDate,"$1年$2月$3日");
  }
  return result;
}

/// <summary>
/// 正则表达式提取和替换内容
/// </summary>
public static string Contentextract()
{
  string result = "";
  string str = "大家好! <User EntryTime='2010-10-7' Email='zhangsan@163.com'>张三</User> 自我介绍。";
  Regex regex = new Regex(@"<User\s*EntryTime='(?<time>[\s\S]*?)'\s+Email='(?<email>[\s\S]*?)'>(?<userName>[\s\S]*?)</User>", RegexOptions.IgnoreCase);
  Match match = regex.Match(str);
  if(match.Success)
  {
    string userName = match.Groups["userName"].Value; //获取用户名
    string time = match.Groups["time"].Value; //获取入职时间
    string email = match.Groups["email"].Value; //获取邮箱地址
    string strFormat = String.Format("我是：{0}，入职时间：{1}，邮箱：{2}", userName, time, email);
    result = regex.Replace(str, strFormat); //替换内容
    Console.WriteLine(result);
  }
  return result;  //结果：大家好！我是张三，入职时间：2010-10-7，邮箱：zhangsan@163.com 自我介绍。
}

/// <summary>
/// 从XML中提取匹配的字段
/// </summary>
/// <param name="args"></param>
static void Main(string[] args)
{
  string strXml = GetStrXml(); //创建用户信息XML
  Regex userRegex = new Regex(@"<User\s*EntryTime='(?<time>[\s\S]*?)'\s+Email='(?<email>[\s\S]*?)'>(?<userName>[\s\S]*?)</User>", RegexOptions.IgnoreCase);
  MatchCollection userMatchColl = userRegex.Matches(strXml);
  if (userMatchColl.Count > 0)
  {
    foreach (Match matchItem in userMatchColl)
    {
      string userName = matchItem.Groups["userName"].Value; //获取用户名
      string time = TransDate(matchItem.Groups["time"].Value); //获取入职时间，并转换日期格式
      string email = CheckMail(matchItem.Groups["email"].Value); //获取邮箱地址，并检测邮箱格式
      string strFormat = String.Format("姓名：{0}，入职时间：{1}，邮箱：{2}", userName, time, email);
      Console.WriteLine(strFormat);
    }
  }
  Console.ReadLine();
}
/// <summary>
/// 创建用户信息XML
/// </summary>
/// <returns></returns>
public static string GetStrXml()
{
  StringBuilder strXml = new StringBuilder();
  strXml.Append("<UserInfo>");
  strXml.Append("<User EntryTime='2010-10-7' Email='zhangsan@163.com'>张三</User>");
  strXml.Append("<User EntryTime='2012-5-15' Email='lisi163.com'>李四</User>");
  strXml.Append("<User EntryTime='2012-6-13' Email='wangwu@qq.com'>王五</User>");
  strXml.Append("</UserInfo>");
  return strXml.ToString();
}