How do I append data to a csv file in C#

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i got this code to insert text into a csv file:

C#

try
               {

                   for (int i = 0; i < this.TestCases; i++)
                   {


                       textClientNumber[i] = readClientNumber.ReadLine();
                       textCardNumber[i] = readCardNumber.ReadLine();

                       export.AddRow();
                       export["TransactionDate"]= DateTime.Now.ToString("yyyyMMdd");
                       export["Card Type"] = "MC";
                       export["Original Payment Reference"] = " ";
                       export["Retreival Reference"] = " ";
                       export["Credit/Debit Card Indicator"] = " ";
                       export["Institution_number"] = this.Institution_number;
                       export["Refund"] = cmbRefund.SelectedItem.ToString();
                       export["Card Number"] = textCardNumber[i].ToString();
                       export["Capture Method"] = cmbCaptureMethod.SelectedValue.ToString();
                       export["ECI Indicator / Rate Program"] = cmbEciIndicator.SelectedItem.ToString();
                       export["Client Number"] = textClientNumber[i].ToString();
                       export["Processor ID"] = " ";
                       export["Currency"] = cmbCurrency.SelectedValue.ToString();
                       int randnum1 = rand.Next(1, 999999);
                       string randnumstring = opClass.AmountToExport(randnum1);
                       export["Amount"] =randnumstring ;
                   }


                   export.ExportToFile("C:\\temp\\MCB2" + randnum + ".csv");
                   this.Excelfilename = "MCB2" + randnum;
                   MessageBox.Show("Csv File created, You can find the file in C:\\temp\\" + this.Excelfilename);

               }
               catch (Exception ex)
               {
                   MessageBox.Show(ex.ToString());
               }

Can someoent ell me how can i begin add rows from the last used row or maybe another technique how to do it ?

What I have tried:

I tried this code to append rows to the exisiting .csv file:

C#

  try
                {
                    StreamReader reader = File.OpenText(this.Excelfilename + ".csv");
                    
                }
                catch (Exception Ex)
                {
                    Console.WriteLine(Ex.ToString());


                var firstLetterCharacters = this.Excelfilename.TakeWhile(Char.IsLetter);
                string filename = new string(firstLetterCharacters.ToArray());
                }




if (filename == "MCB")
            {
                try
                {
                        

                        for (int i = 0; i < this.TestCases; i++)
                        {

                            textClientNumber[i] = readClientNumber.ReadLine();
                            textCardNumber[i] = readCardNumber.ReadLine();

                            export.AddRow();

                            export["TransactionDate"] = DateTime.Now.ToString("yyyyMMdd");
                            export["Card Type"] = "MC";
                            export["Original Payment Reference"] = " ";
                            export["Retreival Reference"] = " ";
                            export["Credit/Debit Card Indicator"] = " ";
                            export["Institution_number"] = this.Institution_number;
                            export["Refund"] = cmbRefund.SelectedItem.ToString();
                            export["Card Number"] = textCardNumber[i].ToString();
                            export["Capture Method"] = cmbCaptureMethod.SelectedValue.ToString();
                            export["ECI Indicator / Rate Program"] = cmbEciIndicator.SelectedItem.ToString();
                            export["Client Number"] = textClientNumber[i].ToString();
                            export["Processor ID"] = " ";
                            export["Currency"] = cmbCurrency.SelectedValue.ToString();
                            int randnum1 = rand.Next(1, 999999);
                            string randnumstring = opClass.AmountToExport(randnum1);
                            export["Amount"] = randnumstring;

                            

                        }
                    if (File.Exists("C:\\temp\\" + this.Excelfilename + ".csv"))
                    {
                        File.Delete(this.Excelfilename);
                        export.ExportToFile("C:\\temp\\" + this.Excelfilename + ".csv");
                    }

everything runs perfectly by the old data will be lost and be replaced to the newest data.

Posted 29-Aug-17 23:09pm

Joe Doe234

Updated 29-Aug-17 23:18pm

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OriginalGriff · Answer 1 · 2017-08-29T23:18:00

Solution 1

You have two methods: you can append the text, using File.AppendText Method (String) (System.IO)[^] or by using a stream with the Append option:

C#

using (FileStream fs = new FileStream(fileName,FileMode.Append, FileAccess.Write))
    {
    using (StreamWriter sw = new StreamWriter(fs))
        {
        sw.WriteLine(myNewCSVLine);
        }
    }

The only other way is to read the entire file (using a string collection, or a CSVReader) append your data, and write it all back to a new file.

Posted 29-Aug-17 23:18pm

OriginalGriff

Comments

Joe Doe234 30-Aug-17 5:23am

Hi OriginalGriff, Thank for helping.

One small question, how can i save "MyNewCsvLine" because i have more than 1 record in that line .

Regards,
Sigmond

OriginalGriff 30-Aug-17 5:34am

Separate them with "\n", or write each line separately in a loop if you have them in a collection.

Or, there is string.Join ... loads of ways, depending on how you have the info stored - which I don't know!

Joe Doe234 30-Aug-17 5:39am

OK thank you :)

OriginalGriff 30-Aug-17 5:42am

You're welcome!