IStateFormatter Interface
Definition
Important
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Defines methods that a type implements to serialize and deserialize an object graph.
public interface class IStateFormatterpublic interface IStateFormattertype IStateFormatter = interfacePublic Interface IStateFormatter- Derived
Examples
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.
namespace Samples.AspNet.CS
{
using System;
using System.IO;
using System.Security.Permissions;
using System.Web;
using System.Web.UI;
//
// 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 : PageStatePersister
{
public StreamPageStatePersister(Page page)
: base(page)
{
}
//
// Load ViewState and ControlState.
//
public override void Load()
{
Stream stateStream = GetSecureStream();
// Read the state string, using the StateFormatter.
StreamReader reader = new StreamReader(stateStream);
IStateFormatter formatter = this.StateFormatter;
string fileContents = reader.ReadToEnd();
// Deserilize returns the Pair object that is serialized in
// the Save method.
Pair statePair = (Pair)formatter.Deserialize(fileContents);
ViewState = statePair.First;
ControlState = statePair.Second;
reader.Close();
stateStream.Close();
}
//
// Persist any ViewState and ControlState.
//
public override void Save()
{
if (ViewState != null || ControlState != null)
{
if (Page.Session != null)
{
Stream stateStream = GetSecureStream();
StreamWriter writer = new StreamWriter(stateStream);
IStateFormatter formatter = this.StateFormatter;
Pair statePair = new Pair(ViewState, ControlState);
// Serialize the statePair object to a string.
string serializedState = formatter.Serialize(statePair);
writer.Write(serializedState);
writer.Close();
stateStream.Close();
}
else
{
throw new InvalidOperationException("Session needed for StreamPageStatePersister.");
}
}
}
// Return a secure Stream for your environment.
private Stream GetSecureStream()
{
// You must provide the implementation to build
// a secure Stream for your environment.
return null;
}
}
}
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
'
' 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
'
' 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
' 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
Remarks
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.
Methods
| Deserialize(String) |
Deserializes an object state graph from its serialized string form. |
| Serialize(Object) |
Serializes ASP.NET Web server control state to string form. |
