ListBox2

-- put into listbox

        private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (listBox1.SelectedItem == null)
            {
                MessageBox.Show("Please select a tab in the listbox.", "Error.", MessageBoxButtons.OK, MessageBoxIcon.Information);
                return;
            }
            textBox1.Text = File.ReadAllText($"./Scripts/{listBox1.SelectedItem}");
        }

-- refresh code

listBox1.Items.Clear();//Clear Items in the ListBox
            Functions.PopulateListBox(listBox1, "./Scripts", "*.txt");
            Functions.PopulateListBox(listBox1, "./Scripts", "*.lua");


-- put into functions

public static void PopulateListBox(ListBox lsb, string Folder, string FileType)
        {
            DirectoryInfo dinfo = new DirectoryInfo(Folder);
            FileInfo[] Files = dinfo.GetFiles(FileType);
            foreach (FileInfo file in Files)
            {
                lsb.Items.Add(file.Name);
            }
        }