Gets or sets whether the bar's visibility can be changed by an end-user. This is a dependency property.
A DefaultBoolean value that specifies if the bar's visibility can be changed by an end-user.
When the DefaultBoolean.Default value is assigned to AllowHide, it's interpreted as follows.
- as False, if the bar's Bar.IsMainMenu or Bar.IsStatusBar property is set to true.
- as True, otherwise.