using System;

using System.Linq;

using System.Collections.Generic;

using System.Text;

using System.Globalization;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string input = @"Datum;Wertstellung;Kategorie;Name;Verwendungszweck;Konto;Bank;Betrag;Währung

31.10.2019;01.11.2019;;Some Text;;;;-42,89;EUR

31.10.2019;01.11.2019;;Some Text;;;;-236,98;EUR

31.10.2019;31.10.2019;;Some Text;;;;-200;EUR

30.10.2019;29.10.2019;;Some Text;;;;204,1;EUR

30.10.2019;31.10.2019;;Some Text;;;;-646,98;EUR";

        string output = ProcessCSVInline(input);

        Console.WriteLine();

        Console.WriteLine("Output CSV:");

        Console.WriteLine(output);

    }

    public enum CsvColumn

    {

        Belegdatum = 0,

        Buchungsdatum = 1,

        Belegnummer = 2,

        Buchungstext = 3,

        Verwendungszweck = 4,

        Soll = 5,

        Haben = 6,

        Betrag = 7,

        Währung = 8

    }

​

    private static string ProcessCSVInline(string csvInput)

    {

        List<string> liste = new List<string>();

        // Build the header row into the output:

        liste.Add("Belegdatum,Buchungsdatum,Belegnummer,Buchungstext,Verwendungszweck,Soll,Haben,Betrag,Währung");

        CultureInfo ci = new CultureInfo("de-DE"); // neccessary only when running the code from other cultures.

​

​

        string line;

​

        // Read the file and display it line by line.  

        try

        {

            // Using StringReader to simulate a StreamReader

            // It has a similar API so most of the code is cut'n'paste ready ;)

            System.IO.StringReader file = new System.IO.StringReader(csvInput);

            int counter = 0;

            while ((line = file.ReadLine()) != null)

            {

                counter++;

                // Input is delimited with ';' so make sure we only split using that character

                var cellArray = Regex.Split(line, @"[;](?=(?:[^\""]|\""[^\""]*\"")*$)")

                    .Select(s => Regex.Replace(s.Replace("\"\"", "\""), "^\"|\"$", "")).ToArray();

​

                // Skip lines that fail for any reason

                try

                {

                    // Check value of Betrag, only operate on it if there is a decimal value there

                    decimal betrag = 0;

                    if (decimal.TryParse(cellArray[(int)CsvColumn.Betrag], NumberStyles.Any, ci, out betrag))

                    {

                        if (betrag >= 0)

                        {

                            cellArray[(int)CsvColumn.Soll] = "42590";

                            cellArray[(int)CsvColumn.Haben] = "441206";

                        }

                        else

                        {

                            cellArray[(int)CsvColumn.Soll] = "441206";

                            cellArray[(int)CsvColumn.Haben] = "42590";

                        }

​

                        // Assuming we only write to the purple field when the green field was a decimal:

                        cellArray[(int)CsvColumn.Belegnummer] = "a dummy text";

                    }

                    else

                    {

                        // Skip lines where the Betrag is not a decimal

                        // this will cover the case when or if the first line is the header.

                        continue;

                    }

                }

                catch(Exception ex)

                {

                    // Construct a message box to help the user resolve the issue.

                    // You can use the MessageBox API to allow the user to cancel the process if you want to extend this.

                    // or remove the message altogether if you want it to silently skip the erroneous rows.

                    // For this Fiddle we are using Console for the output!

                    Console.WriteLine("Fehler beim Analysieren der Eingabezeile,\n" +

                                      ex.Message + "\n\n " +

                                      counter + ":> {line} \n " +

                                      new String(' ', counter.ToString().Length) + " - " + cellArray.Length + " Cells\n " +

                                      "|" + String.Join("|", cellArray) + "|\n " + 

                                      "\n " +

                                      " Zeile wird verworfen, weiter!");

​

                    continue; // advance to the next iteration of the while loop.

                }

​

                // Make sure you escape the columns that have a comma

                liste.Add(string.Join(",", cellArray.Select(x => x.Contains(',') ? "\"" + x + "\"" : x)));

            }

​

            // Using StringBuilder to simplify the processing in .Net Fiddle, we could have used a StringBuilder from the start instead of 

            // the List<string> if you want to. Note that we have to inject the line break though.

            var output = new StringBuilder();

            output.Append(String.Join(Environment.NewLine, liste));

            return output.ToString();

        }

        catch (Exception ex)

        {

            throw new ApplicationException("Der Gewählte Prozess wird bereits von einem anderen verwendet,\n " +

                                           " bitte versuchen sie es erneut", ex);

        }

    }

​

}