asp.net web service executed more than one time - asp.net

Question

I have a web service .asmx that I call from an android mobile application. it return a random number to the android application, and send the same number using sms.
My problem that some times the web service is executed more than one time in the same time and returning the same random number. so the sms is sent more than one time all in one request.
I have two files one is the one I call from my app getRandomNumber.asmx and the second is getRandomNumber.cs the file that generate the number, save to the database and send it by sms.
so i put a log file in both files and waited to the duplicate to show.
this is from a log file I made to track this issue:
Time: 2014/05/24 06:41:46 - user: 610410 - random: Going IN
Time: 2014/05/24 06:41:46 - user: 610410 - random: Going IN
Time: 2014/05/24 06:41:46 - user: 610410 - random: Going IN
Time: 2014/05/24 06:41:46 - user: 610410 - random: Going IN
Time: 2014/05/24 06:41:49 - user: 610410 - random: 853967
Time: 2014/05/24 06:41:49 - user: 610410 - random: 853967
Time: 2014/05/24 06:41:49 - user: 610410 - random: 853967
Time: 2014/05/24 06:41:49 - user: 610410 - random: 853967
what is the cause and how to solve it.
UPDATE: Code added
getRandomNumber.asmx.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Services;
using System.Web.Script.Services;
using System.Web.Script.Serialization;
using OracleDataAccessLayer;
namespace MobileWebServices
{
[WebService(Namespace = "http://www.example.com")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[System.ComponentModel.ToolboxItem(false)]
[System.Web.Script.Services.ScriptService]
public class getRandomNumber : System.Web.Services.WebService
{
[WebMethod]
[ScriptMethod(UseHttpGet = true, ResponseFormat = ResponseFormat.Json)]
public string sendRandomNumber(int UserNumber)
{
Logger.logError("Time: " + DateTime.Now.ToString("yyyy/MM/dd HH:mm:ss") + " - user: " + UserNumber + " - random: Going IN");
return Newtonsoft.Json.JsonConvert.SerializeObject(new getRandomNumber().sendRandomNumber(UserNumber));
}
}
}
getRandomNumber.cs
using System;
using System.Data;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Net;
using System.Text;
using System.IO;
namespace OracleDataAccessLayer
{
public class getRandomNumber : OracleDataAccessLayer.MobileDataAccess.OracleCommandLibrary
{
string sql = "";
public getRandomNumber() { }
string GeneratePasscode(int PasscodeLength)
{
string _allowedChars = "123456789";
Random randNum = new Random();
char[] chars = new char[PasscodeLength];
int allowedCharCount = _allowedChars.Length;
for (int i = 0; i < PasscodeLength; i++)
{
chars[i] = _allowedChars[(int)((_allowedChars.Length) * randNum.NextDouble())];
}
return new string(chars).PadRight(PasscodeLength, '0').ToString();
}
public string sendRandomNumber(int parUserNumber)
{
string random = "0";
string mobile="";
try
{
string randomNum = GeneratePasscode(6);
Logger.logError("Time: " + DateTime.Now.ToString("yyyy/MM/dd HH:mm:ss") + " - user: " + parUserNumber + " - random: " + randomNum);
//select the mobile number and the language
sql = "SELECT C.COUNTRY_LANG, MOBILE " +
"FROM COUNTRY_MASTER_TABLE C " +
"JOIN USER_REG_MASTER U ON " +
"C.COUNTRY_CODE = U.NATIONALITY_NO " +
"WHERE U.UNO = " + parUserNumber;
DataTable lang = Retrievedata(sql);
if (lang.Rows.Count > 0)
{
sql = "INSERT INTO SMS_SEND " +
"(SMS_ID, USER_NUMBER, SMS_DATE, RANDOM, DEVICE_TYPE) VALUES " +
"(SEQ_RANDOM.NEXTVAL, " + parUSERNumber + ", SYSDATE, " + randomNum + ", 1)";
if (ExecuteTransactions(sql) > 0)
{
mobile = lang.Rows[0].ItemArray[1].ToString();
// check the lang Arabic, Non Arabic
// if arabic convert to hex
if (lang.Rows[0].ItemArray[0].ToString() == "A")
{
messageOrg = "الرجاء استخدام الرمز " + randomNum;
Byte[] stringBytes = System.Text.Encoding.UTF8.GetBytes(messageOrg);
StringBuilder sbBytes = new StringBuilder(stringBytes.Length * 2);
foreach (byte bb in stringBytes)
{
sbBytes.AppendFormat("%{0:X2}", bb);
}
message = sbBytes.ToString();
messageHex = message;
}
else
{
// If english do nothing
messageOrg = "Please use this code: " + randomNum;
message = "Please use this code: " + randomNum;
}
// add the message and mobile number to SMS service provider URL and create HttpWebRequest
string url = "http://www.example.com/Send.aspx?MOBILENO=" + mobile + "&MESSAGE=" + message + "&rest of prams";
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.Method = "GET";
// execute request and get response back
using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
{
Stream dataStream = response.GetResponseStream();
StreamReader reader = new StreamReader(dataStream);
smsSequence = reader.ReadToEnd();
reader.Close();
dataStream.Close();
}
// check if success get the response and check id number and insert into SMS_SENTBOX for logging
int success = 0;
if (smsSequence.Substring(0, 3) == "+OK")
//if (Int32.TryParse(smsSequence.Substring(7, smsSequence.Length - 7), out success))
{
random = randomNum;
sql = "INSERT INTO SMS_SENTBOX " +
"(SMS_SENT_SEQUENCE, USER_NUMBER, EVENT_DATE, EVENT_TIME, USER_MOBILE, EVENT_TYPE, SENT_DATE, SMS_TEXT, SMS_TEXT_DUMP)" +
"VALUES " +
"(1, " + parUserNumber + ", SYSDATE, TO_CHAR(SYSDATE, 'HHMI'), " + mobile + ", 'random', SYSDATE, '" + messageOrg + "', '" + messageHex + "')";
try
{
ExecuteTransactions(sql);
}
catch (Exception e)
{
}
}
}
}
}
catch (Exception e)
{
Logger.logError(e.ToString() + "\n");
throw e;
}
return random;
/**/
}
}
}
thankyou

Answer 1

From your description, I don't quite understand whether you have a single problem (the same random number is generated multiple times) or two problems (same random number and request is sent multiple times).
Anyhow, the source of your problem is described in Microsoft's documentation about the Random() constructor:
The default seed value is derived from the system clock and has finite
resolution. As a result, different Random objects that are created in
close succession by a call to the default constructor will have
identical default seed values and, therefore, will produce identical
sets of random numbers.
To fix it, create a single static instance of Random:
static Random random = new Random();
....
string GeneratePasscode(int PasscodeLength)
{
string _allowedChars = "123456789";
char[] chars = new char[PasscodeLength];
int allowedCharCount = _allowedChars.Length;
for (int i = 0; i < PasscodeLength; i++)
{
chars[i] = _allowedChars[(int)((_allowedChars.Length) * random.NextDouble())];
}
return new string(chars).PadRight(PasscodeLength, '0').ToString();
}