protected virtual void OnActiveContentChanged(EventArgs e, IDockContent prevContent)
{
var activeContent = ActiveContent;
EventHandler handler;
if (null != prevContent)
{
prevContent.OnDeactivate(e);
}
handler = (EventHandler)Events[ActiveContentChangedEvent];
if (handler != null)
handler(this, e);
if (null != activeContent)
{
activeContent.OnActivated(e);
}
}