IStateFormatter Interface
Defines methods that a type implements to serialize and deserialize an object graph.
Assembly: System.Web (in System.Web.dll)
'Declaration <AspNetHostingPermissionAttribute(SecurityAction.InheritanceDemand, Level := AspNetHostingPermissionLevel.Minimal)> _ <AspNetHostingPermissionAttribute(SecurityAction.LinkDemand, Level := AspNetHostingPermissionLevel.Minimal)> _ Public Interface IStateFormatter 'Usage Dim instance As IStateFormatter
The IStateFormatter interface defines methods that a type can implement to serialize and deserialize the state that an ASP.NET Web server control maintains in its ViewState property. This infrastructure is used by classes that derive from the PageStatePersister class to maintain an ASP.NET page's state between requests. By default, ASP.NET page state is serialized and deserialized by an instance of the ObjectStateFormatter class; however, site and adapter developers can implement the IStateFormatter interface on their own types to perform this work.
For more information about Web server control state management and view state, see ASP.NET State Management Overview and Dynamic Web Server Controls and View State.
The following code example demonstrates how to create a PageStatePersister object that saves view and control state to a stream on the Web server. The StreamPageStatePersister class demonstrates how to override the Load and Save methods to extract and save page state information. These methods use the IStateFormatter interface inherited from the PageStatePersister class to serialize and deserialize view state. This code example is part of a larger example provided for the PageStatePersister class.
Imports System Imports System.IO Imports System.Security.Permissions Imports System.Web Imports System.Web.UI Namespace Samples.AspNet.VB ' The StreamPageStatePersister is an example view state ' persistence mechanism that persists view and control ' state on the Web server. ' <AspNetHostingPermission(SecurityAction.Demand, Level:=AspNetHostingPermissionLevel.Minimal)> _ Public Class StreamPageStatePersister Inherits PageStatePersister Public Sub New(ByVal page As Page) MyBase.New(page) End Sub 'New ' ' Load ViewState and ControlState. ' Public Overrides Sub Load() Dim stateStream As Stream stateStream = GetSecureStream() ' Read the state string, using the StateFormatter. Dim reader As New StreamReader(stateStream) Dim serializedStatePair As String serializedStatePair = reader.ReadToEnd Dim statePair As Pair Dim formatter As IStateFormatter formatter = Me.StateFormatter ' Deserilize returns the Pair object that is serialized in ' the Save method. statePair = CType(formatter.Deserialize(serializedStatePair), Pair) ViewState = statePair.First ControlState = statePair.Second reader.Close() stateStream.Close() End Sub ' Load ' ' Persist any ViewState and ControlState. ' Public Overrides Sub Save() If Not (ViewState Is Nothing) OrElse Not (ControlState Is Nothing) Then If Not (Page.Session Is Nothing) Then Dim stateStream As Stream stateStream = GetSecureStream() ' Write a state string, using the StateFormatter. Dim writer As New StreamWriter(stateStream) Dim formatter As IStateFormatter formatter = Me.StateFormatter Dim statePair As New Pair(ViewState, ControlState) Dim serializedState As String serializedState = formatter.Serialize(statePair) writer.Write(serializedState) writer.Close() stateStream.Close() Else Throw New InvalidOperationException("Session needed for StreamPageStatePersister.") End If End If End Sub 'Save ' Return a secure Stream for your environment. Private Function GetSecureStream() As Stream ' You must provide the implementation to build ' a secure Stream for your environment. Return Nothing End Function End Class End Namespace
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The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.