enables the ability to navigate through different states of a single piece of source content without reloading the source content for each subsequent navigation.
Assembly: PresentationFramework (in PresentationFramework.dll)
Thetype exposes the following members.
|Equals(Object)||Determines whether the specified object is equal to the current object. (Inherited from Object.)|
|Finalize||Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)|
|GetHashCode||Serves as the default hash function. (Inherited from Object.)|
|GetType||Gets the Type of the current instance. (Inherited from Object.)|
|MemberwiseClone||Creates a shallow copy of the current Object. (Inherited from Object.)|
|Replay||Called to reapply state to a piece of content when navigation occurs.|
|ToString||Returns a string that represents the current object. (Inherited from Object.)|
By default, NavigationService does not store an instance of a content object in navigation history. Instead, NavigationService creates a new instance of the content object each time it is navigated to by using navigation history. This behavior is designed to avoid excessive memory consumption when large numbers and large pieces of content are being navigated to. Consequently, the state of the content is not remembered from one navigation to the next. However, WPF provides the ability to associate a piece of custom state with the navigation history entry for a piece of content.
Custom state that is associated with a navigation history entry must be a class that derives from . You associate a object with a navigation history entry by using one of the following techniques:
Setting NavigatingCancelEventArgs::Content when one of the following events are raised:
By implementing IProvideCustomContentState on the class that wants custom state to be associated with it.
If you call the AddBackEntry method, you must handle the Navigating event or implement IProvideCustomContentState.
When the navigation history entry is navigated to, WPF checks to see if a custom object is associated with it. If so, it calls Replay to allow the custom object to apply the state it remembered from the previous navigation.
A custom class can override JournalEntryName to change the name that appears for the navigation history entry to which the object is associated. The value that JournalEntryName returns is visible from the navigation UI of the various navigators (Internet Explorer 7, NavigationWindow, Frame).
When you store information in custom content state, you cannot store any references to the instance of the page for which you are remembering state if don’t want the content to be retained in memory. This prevents WPF from releasing the page instance, and defeats the purpose of the default navigation history behavior. If you must do this, consider using KeepAlive instead.
Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.