/// <summary>
/// Toggles the control.
/// </summary>
/// <remarks>
/// For this custom control the toggle state is reflected by the color 
/// of the control. This is analogous to the CheckBox IsChecked property.
/// Green   - ToggleState.On
/// Red     - ToggleState.Off
/// Yellow  - ToggleState.Indeterminate
/// </remarks>
void IToggleProvider.Toggle()
{
    ToggleState toggleState = 
        customControl.toggleStateColor[customControl.controlColor];
    // Invoke control method on separate thread to avoid clashing with UI.
    // Use anonymous method for simplicity.
    this.customControl.Invoke(new MethodInvoker(delegate()
    {
        if (toggleState == ToggleState.On)
        {
            customControl.controlColor = Color.Red;
        }
        else if (toggleState == ToggleState.Off)
        {
            customControl.controlColor = Color.Yellow;
        }
        else if (toggleState == ToggleState.Indeterminate)
        {
            customControl.controlColor = Color.Green;
        }
        customControl.Refresh();
    }));
}