Reading CSV File and Generate a text file with chosen columns

Question

Hi everybody,

I am new at programming C#.

I tried every code in the internet. They didn't help me that much. That's why i am here to ask my question:

* I have a .csv file with following headers: Name, Surname, Age, Date of Birth, Place

* I want to generate a text file with 3 columns: Name, Surname and Age

How can i generate such a file? I started to program following code just to generate everything as text file. It doesn't work. It generates only an empty text file.. I don't know why..

namespace CsvOkuma2
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        OpenFileDialog filedialog = new OpenFileDialog();
        StreamWriter File = new StreamWriter("NewText.txt");

        private void ButtonGenerate(object sender, EventArgs e)
        {
            using (StreamReader sr = new StreamReader(FileAddress.Text, Encoding.Default) )
            {
                readWriteInfo(sr);
            }
        }

        private void Button_Select(object sender, EventArgs e)
        {
            SelectFile(FileAddress);
        }

        private void readWriteInfo(StreamReader sr)
        {
            string currentLine;

            while ( ( currentLine = sr.ReadLine() ) != null )

            { File.Write(currentLine); }

        }

        private void SelectFile(TextBox tb, string filter = "CSV files|*.csv|Alle|*.*",
            bool fileMustExist = true)
        {
            filedialog.Filter = filter;
            filedialog.CheckFileExists = fileMustExist;

            if (DialogResult.OK == filedialog.ShowDialog())
            {
                tb.Text = filedialog.FileName;
            }
        }
    }
}

Answer 1

You will need to call Flush and Close method on StreamWriter for it :

while ( ( currentLine = sr.ReadLine() ) != null )
{ 
    File.Write(currentLine); 
   
    File.Flush();
}
File.Close();

or you will need to set AutoFlush property to true instead :

StreamWriter File = new StreamWriter("NewText.txt");
File.AutoFlush = true;

As it implements IDisposable, it's more better to use it with using block :

using (StreamWriter File = new StreamWriter("NewText.txt"))
{
    while ( ( currentLine = sr.ReadLine() ) != null )
    { 
        File.Write(currentLine); 
   
         File.Flush();
    }

}

You can also take a look at the following post that would be helpful too:

https://stackoverflow.com/questions/11023868/streamwriter-write-doesnt-write-to-file-no-exception-thrown

Hope it helps!

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Answer 2

Thank you so much, that helped me a lot to solve my problem. I learned a new thing with your help! I appreciate!

Could you also tell me how i can save single columns like: write only Name, Surname and Age Columns?

Answer 3

Hi CanAcarDUS,

Try the code below to get the single columns. You could set the column you want in columnName string array in the code.

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Configuration;
using System.Data;
using System.Data.OleDb;
using System.Data.SqlClient;
using System.Diagnostics;
using System.Diagnostics.Eventing.Reader;
using System.DirectoryServices;
using System.DirectoryServices.AccountManagement;
using System.IO;
using System.IO.Ports;
using System.Linq;
using System.Management;
using System.Runtime.InteropServices;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using System.Xml;
using System.Xml.Linq;
using System.Xml.XPath;

namespace ConsoleApp
{
    public class Program
    {
        public static void Main(string[] args)
        {
            ////create a csv file
            //string filePath = @"test.csv";
            //string delimiter = ",";
            //string[][] output = new string[][]{
            //       new string[]{"Name", "Surname", "Age","Date of Birth","Place"},
            //       new string[]{"Apple", "A", "10","1990/3/4","USA" },
            //       new string[]{"Bob", "B", "11","1991/3/4","China" },
            //       new string[]{"Cherry", "C", "12","1992/3/4","Japan" }
            //   };
            //int length = output.GetLength(0);
            //StringBuilder sb = new StringBuilder();
            //for (int index = 0; index < length; index++)
            //    sb.AppendLine(string.Join(delimiter, output[index]));
            //File.WriteAllText(filePath, sb.ToString());

            //comvert vsc to datatable
            var table = ConvertCSVtoDataTable("test.csv");

            //get value of special column
            string[] columnName = { "Name", "Surname", "Age" };

            for (int i = table.Columns.Count - 1; i >= 0; i--)
            {
                DataColumn dc = table.Columns[i];
                if (!columnName.Contains(dc.ColumnName))
                {
                    table.Columns.Remove(dc);
                }
            }

            WriteDataToFile(table, "datatable.txt");
        }
        public static DataTable ConvertCSVtoDataTable(string strFilePath)
        {
            StreamReader sr = new StreamReader(strFilePath);
            string[] headers = sr.ReadLine().Split(',');
            DataTable dt = new DataTable();
            foreach (string header in headers)
            {
                dt.Columns.Add(header);
            }
            while (!sr.EndOfStream)
            {
                string[] rows = Regex.Split(sr.ReadLine(), ",(?=(?:[^\"]*\"[^\"]*\")*[^\"]*$)");
                DataRow dr = dt.NewRow();
                for (int i = 0; i < headers.Length; i++)
                {
                    dr[i] = rows[i];
                }
                dt.Rows.Add(dr);
            }
            return dt;
        }

        public static void WriteDataToFile(DataTable submittedDataTable, string submittedFilePath)
        {
            int i = 0;
            StreamWriter sw = null;

            sw = new StreamWriter(submittedFilePath, false);

            for (i = 0; i < submittedDataTable.Columns.Count - 1; i++)
            {

                sw.Write(submittedDataTable.Columns[i].ColumnName + ";");

            }
            sw.Write(submittedDataTable.Columns[i].ColumnName);
            sw.WriteLine();

            foreach (DataRow row in submittedDataTable.Rows)
            {
                object[] array = row.ItemArray;

                for (i = 0; i < array.Length - 1; i++)
                {
                    sw.Write(array[i].ToString() + ";");
                }
                sw.Write(array[i].ToString());
                sw.WriteLine();

            }

            sw.Close();
        }
    }
}

Best Regards,

Wendy

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Answer 4

You are amazing! Thank you so much!