Get chosen listbox text to show in richtextbox with custom text

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C#

ListBox

RichTextBox

Hi there,

I'm making a bible book app where I have listbox, richtextbox and search textbox.

I have som problem coding when the listbox text is chosen, It will show the listbox text + custom text in richtextbox.

I have done this:

private void btnAra_Click(object sender, EventArgs e)
    {
        int index = 0;
        String temp = richTextBox1.Text;
            richTextBox1.Text = "";
        richTextBox1.Text = temp;

        while (index < richTextBox1.Text.LastIndexOf(txtAra.Text))
        {
            richTextBox1.Find(txtAra.Text, index, richTextBox1.TextLength, RichTextBoxFinds.None);
            richTextBox1.SelectionBackColor = Color.Orange;
            index = richTextBox1.Text.IndexOf(txtAra.Text, index) + 1;
        }
    }

But since this is going to be a book app, I want the chosen listbox to show a text file in richtexbox and not only 2-3 sentences..

Any tip for what I can do?

Updated with this:

private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
      {


          var str = listBox1.SelectedItem.ToString();
          if (str == "    Yaratılış        Tevrat")
          {
              richTextBox1.Text = str + "\t\r\n\nText here";
          }
          else if (str == "    Mısır'dan Çıkış              (Yasa)")
          {
              richTextBox1.Text = str + "\t\r\n\ncustom text 2";
          }