1,先将15位的号码变成18位
private string per15To18(string perIDSrc) 
        {
            int iS = 0;
            //加权因子常数 
            int[] iW=new int[]{7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2};
            //校验码常数 
            string LastCode="10X98765432"; 
            //新身份证号 
            string perIDNew; 
 
            System.Text.RegularExpressions.Regex rg = new System.Text.RegularExpressions.Regex(@"^\d{15}$");
            System.Text.RegularExpressions.Match mc = rg.Match(perIDSrc);
            if(!mc.Success)
            {
                MessageBox.Show("位数不正确！");
                return "";
            }   
            perIDNew=perIDSrc.Substring(0,6);
            //填在第6位及第7位上填上‘1’，‘9’两个数字 
            perIDNew += "19"; 
 
            perIDNew += perIDSrc.Substring(6,9); 
 
            //进行加权求和 
            for( int i=0; i<17; i++) 
            { 
                iS += int.Parse(perIDNew.Substring(i,1)) * iW[i];
            } 
     
            //取模运算，得到模值 
            int iY = iS%11; 
            //从LastCode中取得以模为索引号的值，加到身份证的最后一位，即为新身份证号。 
            perIDNew += LastCode.Substring(iY,1); 
            MessageBox.Show(perIDNew);
            return perIDNew;
        } 

2,校验号码
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|x)$");
            System.Text.RegularExpressions.Match mc = rg.Match(cid);
            if(!mc.Success)
            {
                MessageBox.Show("位数不正确！");
                return "";
            }   
            cid = cid.ToLower();
            cid = cid.Replace("x","a");
            if(aCity[int.Parse(cid.Substring(0,2))]==null)
            {
                MessageBox.Show("非法地区");
                return "非法地区";
            }
            try
            {
                DateTime.Parse(cid.Substring(6,4)+"-"+cid.Substring(10,2)+"-"+cid.Substring(12,2));
            }
            catch
            {
                MessageBox.Show("非法生日");
                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)
            {
                MessageBox.Show("非法证号");
                return("非法证号");
            }
            MessageBox.Show((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")));
            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"));
  
//            return null;
}

3,完成