c# clear textbox
private void button2_Click(object sender, EventArgs e)
    {
        //add pgs selected to array, array needs to be global? combobox1 accCollection.Items.Add(value);
        textbox18.text = "";
        pgHolder[pgCount] = comboBox1.Text + ", "; // error here why?
        pgCount++;

        foreach(string Pg in pgHolder)
        {
            pgTemp = Pg;
            pgHolder1 += pgTemp;
        }

        textBox18.Text = pgHolder1;
    }

OR