Why is my oracledatareader fetching only 1 random row

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I have a program that retrieves valid email addresses from an Oracle database table and writes them to a text file. When i run the program i am only getting 1 random row instead of up 300000+ rows. When i step through the code i can see that the value returned is repeated on all the rows returned.

This is my code for retrieving :

C#

<pre>
  List<Flex> details = new List<Flex>();
try
            {

                using (OracleConnection connp = new OracleConnection(FCUBSConnection))
                {
                    connp.Open();                 
                    OracleCommand cmd1 = new OracleCommand("SELECT FCPREPROD.STTM_CUST_PERSONAL.CUSTOMER_NO,FCPREPROD.STTM_CUST_PERSONAL.MOBILE_NUMBER,FCPREPROD.STTM_CUST_PERSONAL.LAST_NAME,FCPREPROD.STTM_CUST_PERSONAL.E_MAIL,FCPREPROD.STTM_CUST_PERSONAL.FIRST_NAME,FCPREPROD.STTM_CUSTOMER.LOCAL_BRANCH  FROM FCPREPROD.STTM_CUST_PERSONAL INNER JOIN FCPREPROD.STTM_CUSTOMER ON FCPREPROD.STTM_CUST_PERSONAL.CUSTOMER_NO = FCPREPROD.STTM_CUSTOMER.CUSTOMER_NO", connp);                 
                    OracleDataReader dr1 = cmd1.ExecuteReader();
                    
                    while ( dr1.Read())
                    {
                        var model = new Flex();
                        model.EmailAddress = Convert.ToString(dr1["E_MAIL"]);
                        model.FirstName = Convert.ToString(dr1["FIRST_NAME"]);
                        model.LastName = Convert.ToString(dr1["LAST_NAME"]);
                        model.MobileNo = Convert.ToString(dr1["MOBILE_NUMBER"]);
                        model.CustNo = Convert.ToString(dr1["CUSTOMER_NO"]);
                        details.Add(model);
                    }
                  
                    connp.Close();
                }                

                foreach (var email in details)
                {

                 

                    if (!string.IsNullOrEmpty(email.EmailAddress) && IsValidEmail(email.EmailAddress))
                    {
                     
                        //write recipients to logfile
                        string realPath = @"C:\Users\tshumae\Documents\";
                        string appLog = "SSP_EMAILS";
                        var logPath = realPath + Convert.ToString(appLog) + DateTime.Today.ToString("dd -MM-yy") + ".txt";
                        try
                        {
                            if (!File.Exists(logPath))
                        {
                            File.Create(logPath).Dispose();

                            using (StreamWriter sw = File.AppendText(logPath))
                            {
                                sw.WriteLine(email.EmailAddress + " " + email.LastName);
                                sw.Flush();
                                sw.Close();
                            }
                        }
                    }
                        catch (UnauthorizedAccessException ex)
                    {

                    }

                }
            }

            }
            catch (Exception ex)
            {
                ExceptionLogger.SendErrorToText(ex);
            }

What am i missing ? It appears there is some transformation that is occuring as the DataReader loops through records and adds them to details

What I have tried:

I have tried moving the model out of the while loop as below but i still get 1 row instead :

C#

var model = new Flex();
                    while ( dr1.Read())
                    {
                        
                        model.EmailAddress = Convert.ToString(dr1["E_MAIL"]);
                        model.FirstName = Convert.ToString(dr1["FIRST_NAME"]);
                        model.LastName = Convert.ToString(dr1["LAST_NAME"]);
                        model.MobileNo = Convert.ToString(dr1["MOBILE_NUMBER"]);
                        model.CustNo = Convert.ToString(dr1["CUSTOMER_NO"]);
                        details.Add(model);
                    }

Posted 29-Oct-20 23:28pm

Tshumore

Updated 29-Oct-20 23:35pm

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OriginalGriff · Answer 1 · 2020-10-29T23:35:00

Why? Because you told it to.
You create a single instance of the Flex class then add it multiple times to yoru collection, overwriting the previous data each time roudn the loop.

If I simplify what you have done it may be clearer:

C#

int x;
for (i = 0; i < 5; i++)
   {
   x = i;
   }
Console.WriteLine(x);

Would you expect the print to contain "0, 1, 2, 3, 4" or just "4"?

You've done the same thing - move the constructor inside the loop, and it'll add different values:

C#

while ( dr1.Read())
{
    var model = new Flex();
    model.EmailAddress = Convert.ToString(dr1["E_MAIL"]);
    model.FirstName = Convert.ToString(dr1["FIRST_NAME"]);
    model.LastName = Convert.ToString(dr1["LAST_NAME"]);
    model.MobileNo = Convert.ToString(dr1["MOBILE_NUMBER"]);
    model.CustNo = Convert.ToString(dr1["CUSTOMER_NO"]);
    details.Add(model);
}