/// <summary>Raises the <see cref="E:System.Windows.Forms.CheckBox.CheckStateChanged" /> event.</summary>
/// <param name="e">An <see cref="T:System.EventArgs" /> that contains the event data. </param>
protected override void OnCheckStateChanged(EventArgs e)
{
bool?checkedValue = CheckState == CheckState.Indeterminate
? (bool?)null
: (CheckState == CheckState.Checked);
PCheckBox.SetModelValue(this, PCheckBox.IsCheckedProperty, checkedValue, EBindingSourceUpdateReason.PropertyChanged);
base.OnCheckStateChanged(e);
}