c# 檢查身分證

protected bool IdCheck(string strUserID)
    {
      int intAreaNo=0; //區域碼變數。
      int intCheckSum=0;//檢核碼變數。
      int intCount=0;//計數變數。
      string strAreaCode;//區域碼變數。 
        //轉換為大寫。
        strUserID = strUserID.ToString().ToUpper();
        //取得首碼字母。
        strAreaCode = strUserID.Substring(0,1);  
        //設定起始值。
        bool check  = false;
        //確定身份證有10碼。
        if(strUserID.Length == 10)
        {
          //確定首碼在A-Z之間。
            if (IsNatural_Number(strAreaCode))
            {
              //確定第二碼是數字 1 或 2。(1為男生, 2為女生)
              if (strUserID.Substring(1, 1) == "1" || strUserID.Substring(1, 1) == "2")
              {
                      //取得英文字母對應編號。A -> 10, B -> 11 等等。
                      string abc = "ABCDEFGHJKLMNPQRSTUVXYWZIO";
                      for (int i = 0; i < abc.Length; i++)
                      {
                          if (strAreaCode == abc.Substring(i, 1))
                          {
                              intAreaNo = i + 10;
                          }
                      }
                       strUserID = intAreaNo.ToString() + strUserID.Substring(1, 9);
                       int count=0;
                        for (int j = 10; j >= 0; j--)
                        {
                            if (j == 0)
                            {
                                count += Convert.ToInt32(strUserID.ToString().Substring(10, 1)) * 1; 
                            }
                            else
                            {
                                int a = strUserID.Length - j - 1;
                                count += Convert.ToInt32(j.ToString().Substring(0, 1)) * Convert.ToInt32(strUserID.Substring(a,1));
                            }
                        }
                        if ((count * 1.0) % 10 == 0)
                        {
                            check = true;
                        }   
              }
              else
              {

              }
          }
          else
          {

          }
        }
        else
        {

        }
        return check;
    }



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