C# combobox (search anywhere within list, not just first letter )

private void comboBox1_KeyUp(object sender, KeyEventArgs e)
        {
            //index of taped text
            int index;
            //text found
            string found;
            //text written
            string actual;

            //to avoid these keys
            bool bo = e.KeyCode == Keys.Back || e.KeyCode == Keys.Left
            || e.KeyCode == Keys.Right || e.KeyCode == Keys.Up || e.KeyCode == Keys.Down
            || e.KeyCode == Keys.Delete || e.KeyCode == Keys.PageDown
            || e.KeyCode == Keys.PageUp || e.KeyCode == Keys.End
            || e.KeyCode == Keys.Home;

            if (bo == true)
                return;

            actual = this.comboBox1.Text;
            index = this.comboBox1.FindString(actual);

            //this condition means that there is a result
            if (index > -1)
            {
                found = this.comboBox1.Items[index].ToString();
                this.comboBox1.SelectedIndex = index;

                this.comboBox1.SelectionStart = actual.Length;
                this.comboBox1.SelectionLength = found.Length;
                this.comboBox1.DroppedDown = true;

            }
        }