void OnPreviewInvoke(object sender, PreviewInvokeEventArgs e)
{
DataBindingHelper.EnsureDataBindingOnActionsUpToDate(this);
}
/// <summary>
/// Ensure that any binding on DP operands are up-to-date.
/// </summary>
private void EnsureBindingUpToDate()
{
DataBindingHelper.EnsureBindingUpToDate(this, LeftOperandProperty);
DataBindingHelper.EnsureBindingUpToDate(this, OperatorProperty);
DataBindingHelper.EnsureBindingUpToDate(this, RightOperandProperty);
}