/// <summary>
 /// Constructs the <see cref="ExtensionItemEventArgs"/> that just require an action.
 /// </summary>
 public ExtensionItemEventArgs(ExtensionItemAction action)
 {
     Action = action;
     Index  = -1;
 }
 /// <summary>
 /// Constructs the <see cref="ExtensionItemEventArgs"/> that require an action and index.
 /// </summary>
 public ExtensionItemEventArgs(ExtensionItemAction action, int index)
 {
     Action = action;
     Index  = index;
 }
 protected void RaiseChanged(ExtensionItemAction action, int index)
 {
     Changed?.Invoke(this, new ExtensionItemEventArgs(action, index));
 }