/// <summary>
    /// 验证身份证是否合法
    /// </summary>
    /// <param name="idCard">要验证的身份证</param>    
    public static bool IsIdCard(string idCard)
    {
      //如果为空，认为验证合格
      if (IsNullOrEmpty(idCard))
      {
        return true;
      }
 
      //清除要验证字符串中的空格
      idCard = idCard.Trim();
 
      //模式字符串
      StringBuilder pattern = new StringBuilder();
      pattern.Append(@"^(11|12|13|14|15|21|22|23|31|32|33|34|35|36|37|41|42|43|44|45|46|");
      pattern.Append(@"50|51|52|53|54|61|62|63|64|65|71|81|82|91)");
      pattern.Append(@"(\d{13}|\d{15}[\dx])$");
 
      //验证
      return RegexHelper.IsMatch(idCard, pattern.ToString());
    }

private string CheckCidInfo(string cid)
 {
  string[] aCity = new string[]{null,null,null,null,null,null,null,null,null,null,null,"北京","天津","河北","山西","内蒙古",null,null,null,null,null,"辽宁","吉林","黑龙江",null,null,null,null,null,null,null,"上海","江苏","浙江","安微","福建","江西","山东",null,null,null,"河南","湖北","湖南","广东","广西","海南",null,null,null,"重庆","四川","贵州","云南","西藏",null,null,null,null,null,null,"陕西","甘肃","青海","宁夏","新疆",null,null,null,null,null,"台湾",null,null,null,null,null,null,null,null,null,"香港","澳门",null,null,null,null,null,null,null,null,"国外"};
  double iSum=0;
  string info="";
  System.Text.RegularExpressions.Regex rg = new System.Text.RegularExpressions.Regex(@"^\d{17}(\d|x)$");
  System.Text.RegularExpressions.Match mc = rg.Match(cid);
  if(!mc.Success)
  {
  return "";
  }  
  cid = cid.ToLower();
  cid = cid.Replace("x","a");
  if(aCity[int.Parse(cid.Substring(0,2))]==null)
  {
  return "非法地区";
  }
  try
  {
  DateTime.Parse(cid.Substring(6,4)+"-"+cid.Substring(10,2)+"-"+cid.Substring(12,2));
  }
  catch
  {
  return "非法生日";
  }
  for(int i=17;i>=0;i--)
  {  
  iSum +=(System.Math.Pow(2,i)%11)*int.Parse(cid[17-i].ToString(),System.Globalization.NumberStyles.HexNumber);

  }
  if(iSum%11!=1)
  return("非法证号");
  
  return(aCity[int.Parse(cid.Substring(0,2))]+","+cid.Substring(6,4)+"-"+cid.Substring(10,2)+"-"+cid.Substring(12,2)+","+(int.Parse(cid.Substring(16,1))%2==1¡"男":"女"));
 
 }

调用测试：
Response.Write(CheckCidInfo("340524198002300019"));
Response.Write(CheckCidInfo("34052419800101001x"));

/// <summary>
/// 身份证验证
/// </summary>
/// <param name="Id">身份证号</param>
/// <returns></returns>
public bool CheckIDCard(string Id)
{
  if (Id.Length == 18)
  {
     bool check = CheckIDCard18(Id);
     return check;
   }
   else if (Id.Length == 15)
   {
     bool check = CheckIDCard15(Id);
     return check;
   }
   else
   {
     return false;
   }
 }
 /// <summary>
 /// 18位身份证验证
 /// </summary>
 /// <param name="Id">身份证号</param>
 /// <returns></returns>
 PRivate bool CheckIDCard18(string Id)
 {
   long n = 0;
   if (long.TryParse(Id.Remove(17), out n) == false || n < Math.Pow(10, 16) || long.TryParse(Id.Replace('x', '0').Replace('X', '0'), out n) == false)
   {
     return false;//数字验证
   }
   string address = "11x22x35x44x53x12x23x36x45x54x13x31x37x46x61x14x32x41x50x62x15x33x42x51x63x21x34x43x52x64x65x71x81x82x91";
   if (address.IndexOf(Id.Remove(2)) == -1)
   {
     return false;//省份验证
   }
   string birth = Id.Substring(6, 8).Insert(6, "-").Insert(4, "-");
   DateTime time = new DateTime();
   if (DateTime.TryParse(birth, out time) == false)
   {
     return false;//生日验证
   }
   string[] arrVarifyCode = ("1,0,x,9,8,7,6,5,4,3,2").Split(',');
   string[] Wi = ("7,9,10,5,8,4,2,1,6,3,7,9,10,5,8,4,2").Split(',');
   char[] Ai = Id.Remove(17).ToCharArray();
   int sum = 0;
   for (int i = 0; i < 17; i++)
   {
     sum += int.Parse(Wi[i]) * int.Parse(Ai[i].ToString());
   }
   int y = -1;
   Math.DivRem(sum, 11, out y);
   if (arrVarifyCode[y] != Id.Substring(17, 1).ToLower())
   {
     return false;//校验码验证
   }
   return true;//符合GB11643-1999标准
 }
 /// <summary>
 /// 15位身份证验证
 /// </summary>
 /// <param name="Id">身份证号</param>
 /// <returns></returns>
 private bool CheckIDCard15(string Id)
 {
   long n = 0;
   if (long.TryParse(Id, out n) == false || n < Math.Pow(10, 14))
   {
     return false;//数字验证
   }
   string address = "11x22x35x44x53x12x23x36x45x54x13x31x37x46x61x14x32x41x50x62x15x33x42x51x63x21x34x43x52x64x65x71x81x82x91";
   if (address.IndexOf(Id.Remove(2)) == -1)
   {
     return false;//省份验证
   }
   string birth = Id.Substring(6, 6).Insert(4, "-").Insert(2, "-");
   DateTime time = new DateTime();
   if (DateTime.TryParse(birth, out time) == false)
   {
     return false;//生日验证
   }
   return true;//符合15位身份证标准
 }