How to populate a textbox from toolstripcombobox?

I have a custom combobox (ButtonDropDown using Custom Control (ButtonDropDownMenu Control)[^])control that I have filled with some filenames from a listarray, but now I would like it if I clicked on a filename that this filename loads into the textbox.

This is the code I got so far.

private void buttonDutch_Click(object sender, EventArgs e)
        {
            string[] Filelistarray = Directory.GetFiles(@"C:\Users\a961835\Programming", "*.txt");
            List<string> fileNames = new List<string>();
            foreach (string FileName in Filelistarray)
            {
                string filenameWithoutPath = Path.GetFileName(FileName);
                fileNames.Add(filenameWithoutPath);
            }

            toolStripComboBox1.Items.AddRange(fileNames.ToArray());



        }

        private void ComboBox_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (toolStripComboBox1.SelectedIndex > 0)
            {
                this.textBox1.Text = toolStripComboBox1.SelectedItem.ToString();
            }
        }

Anyone who has an idea how to do this?

Tags: C# (C# 3.0, C# 4.0), Text