DISPLAY the first index of every line in a text file, in a listbox c#

Hi all, I'm trying to display the first index of each line in my text file, but i'm slow on success.

My code is doing 2 things that is undesirable to me.

1: it replaces the line instead of adding a new line when I add the data, and 2: It duplicates the first line 6 times when it loads. I need help to ensure that it saves the data right and then displays it correctly. Here is my current code:

private void butaddsup_Click(object sender, EventArgs e)//This is the button that adds my data
        {
            if (textsupname.Text != "" || textnumb.Text != "")
            {
                string path = @"data\Suppliers.txt";
                if (!File.Exists(path))
                {
                    File.Create(path);
                    TextWriter supWriter = new StreamWriter(path);
                    supWriter.Write(textsupname.Text + ",");
                    supWriter.Write(textnumb.Text + ",");
                    if (checdiscr1.Checked == true) { supWriter.Write(textdescr1.Text + ","); } else { supWriter.Write("0" + ","); }
                    if (textdescr1.Enabled == true && textdescr1.Text == "") { supWriter.Write("0" + ","); }
                    if (checdiscr2.Checked == true) { supWriter.Write(textdescr2.Text + ","); } else { supWriter.Write("0" + ","); }
                    if (textdescr2.Enabled == true && textdescr2.Text == "") { supWriter.Write("0" + ","); }
                    if (checdiscr3.Checked == true) { supWriter.Write(textdescr3.Text + ","); } else { supWriter.Write("0" + ","); }
                    if (textdescr3.Enabled == true && textdescr3.Text == "") { supWriter.Write("0" + ","); }
                    if (checdiscr4.Checked == true) { supWriter.Write(textdescr4.Text + ","); } else { supWriter.Write("0" + ","); }
                    if (textdescr4.Enabled == true && textdescr4.Text == "") { supWriter.Write("0" + ","); }
                    if (checdiscr5.Checked == true) { supWriter.Write(textdescr5.Text + ","); } else { supWriter.Write("0"); }
                    if (textdescr5.Enabled == true && textdescr5.Text == "") { supWriter.Write("0" + ","); }
                    MessageBox.Show("Details have been saved");
                    supWriter.Close();
                }
                else if (File.Exists(path))
                {
                    using (var supWriter = new StreamWriter(path, true))
                    {
                        supWriter.Write(textsupname.Text + ",");
                        supWriter.Write(textnumb.Text + ",");
                        if (checdiscr1.Checked == true) { supWriter.Write(textdescr1.Text + ","); } else { supWriter.Write("0" + ","); }
                        if (textdescr1.Enabled == true && textdescr1.Text == "") { supWriter.Write("0" + ","); }
                        if (checdiscr2.Checked == true) { supWriter.Write(textdescr2.Text + ","); } else { supWriter.Write("0" + ","); }
                        if (textdescr2.Enabled == true && textdescr2.Text == "") { supWriter.Write("0" + ","); }
                        if (checdiscr3.Checked == true) { supWriter.Write(textdescr3.Text + ","); } else { supWriter.Write("0" + ","); }
                        if (textdescr3.Enabled == true && textdescr3.Text == "") { supWriter.Write("0" + ","); }
                        if (checdiscr4.Checked == true) { supWriter.Write(textdescr4.Text + ","); } else { supWriter.Write("0" + ","); }
                        if (textdescr4.Enabled == true && textdescr4.Text == "") { supWriter.Write("0" + ","); }
                        if (checdiscr5.Checked == true) { supWriter.Write(textdescr5.Text + ","); } else { supWriter.Write("0"); }
                        if (textdescr5.Enabled == true && textdescr5.Text == "") { supWriter.Write("0" + ","); }
                        MessageBox.Show("Details have been saved");
                        supWriter.Close();
                    }
                }
            }
            else
            {
                MessageBox.Show("Please enter All Required Fields\n marked with a *");
            }
            textsupname.Text = "";
            textnumb.Text = "";
            textdescr1.Text = "";
            textdescr2.Text = "";
            textdescr3.Text = "";
            textdescr4.Text = "";
            textdescr5.Text = "";

            if (checdiscr1.Checked == true) { checdiscr1.Checked = false; }
            if (checdiscr2.Checked == true) { checdiscr2.Checked = false; }
            if (checdiscr3.Checked == true) { checdiscr3.Checked = false; }
            if (checdiscr4.Checked == true) { checdiscr4.Checked = false; }
            if (checdiscr5.Checked == true) { checdiscr5.Checked = false; }

        }

private void suppliersToolStripMenuItem_Click(object sender, EventArgs e)//Click event to populate listbox listsup
        {
            listsup.Text = "";
            FormControl();
            SupGB.Visible = true;
            SupGB.BringToFront();
            Optionchc.Visible = false;
            mainFormHandler.Size = new System.Drawing.Size(310, 367);
            int Counter = 0;
            StreamReader supReader = new StreamReader(@"data\Suppliers.txt", true);
                while (!supReader.EndOfStream)
                {
                    string line = supReader.ReadLine();
                    string[] tokens = line.Split(new char[] { ',' }, StringSplitOptions.None);
                    foreach (string s in tokens)
                    {
                        if (listsup.Items.Contains(tokens) == false)
                        {
                            listsup.Items.Add(tokens[0]);
                        Counter++;
                        }
                    }
                }
            supReader.Close();

        }