WPF-005: Use of KeepAlive in the PageFunction navigation

For Page navigation, you can directly use this. NavigationService. Navigate (New Page Object, parameter (optional), but to better process the returned results. It is best to use the Page that inherits PageFunction <T> to navigate and process the Return of a Page in the Return event. Note: 1. default constructor and constructor with parameters. If KeepAlive is not set, the constructor is called again when the new page is returned, and the default value is called. 2. When there is only one constructor with parameters, there is only one constructor with parameters, and KeepAlive is not set. When a new page returns (OnReturn), an exception is reported: you have not set the object reference to the instance of the object. 1. When using constructors with parameters, you must set KeepAlive = true on this page. 2. It is best to have only one default constructor for a page. The parameter is passed when you Navigate to the page (this. NavigationService. Navigate (New Page Object, parameter (optional ))). However, when KeepAlive = true is set, pay attention to the values that need to be processed at the time of return. Otherwise, the old data will affect the data on the current interface.