public int Interval {get; set;}

// Returns a SpinButton instance for gcComboFrame1.
private SideButtonBase CreateSpinButton()
{
    SpinButton spinButton = new SpinButton();

    // Specify a unique name for this button.
    spinButton.Name = "SpinButton";

    // Set the Interval for spinButton.
    spinButton.Interval = 100;

    spinButton.SpinUp += new EventHandler(SpinButton_SpinUp);
    spinButton.SpinDown += new EventHandler(SpinButton_SpinDown);

    // Not show spinButton in gcComboFrame1.
    spinButton.Visible = ButtonVisibility.NotShown;

    return spinButton;
}

// Increase the seleced index of listBox1 when spin is down.
private void SpinButton_SpinDown(object sender, EventArgs e)
{
    if (this.listBox1.SelectedIndex < this.listBox1.Items.Count - 1)
    {
        this.listBox1.SelectedIndex += 1;
    }
    else
    {
        this.listBox1.SelectedIndex = this.listBox1.Items.Count - 1;
    }

    this.textBox1.Text = this.listBox1.SelectedItem.ToString();
}

// Decrease the seleced index of listBox1 when spin is down.
private void SpinButton_SpinUp(object sender, EventArgs e)
{
    if (this.listBox1.SelectedIndex > 0)
    {
        this.listBox1.SelectedIndex -= 1;
    }
    else
    {
        this.listBox1.SelectedIndex = 0;
    }
    this.textBox1.Text = this.listBox1.SelectedItem.ToString();
}