HiddenFieldPageStatePersister Class

Reference

Definition

Namespace:: System.Web.UI

Assembly:: System.Web.dll

Important

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Stores ASP.NET page view state on the Web client in a hidden HTML element.

public ref class HiddenFieldPageStatePersister : System::Web::UI::PageStatePersister

public class HiddenFieldPageStatePersister : System.Web.UI.PageStatePersister

type HiddenFieldPageStatePersister = class
    inherit PageStatePersister

Public Class HiddenFieldPageStatePersister
Inherits PageStatePersister

Inheritance: Object

PageStatePersister
HiddenFieldPageStatePersister

Examples

The following code example demonstrates how to bind a ListBox control to data in a database with a SqlDataSource control.

<%@ Page language="C#" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>ASP.NET Example</title>
</head>
<body>
    <form id="form1" runat="server">
      <asp:SqlDataSource
          id="SqlDataSource1"
          runat="server"
          DataSourceMode="DataReader"
          ConnectionString="<%$ ConnectionStrings:MyNorthwind%>"
          SelectCommand="SELECT LastName FROM Employees">
      </asp:SqlDataSource>

      <asp:ListBox
          id="ListBox1"
          runat="server"
          DataTextField="LastName"
          DataSourceID="SqlDataSource1">
      </asp:ListBox>

    </form>
  </body>
</html>

<%@ Page language="VB" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>ASP.NET Example</title>
</head>
<body>
    <form id="form1" runat="server">
      <asp:SqlDataSource
          id="SqlDataSource1"
          runat="server"
          DataSourceMode="DataReader"
          ConnectionString="<%$ ConnectionStrings:MyNorthwind%>"
          SelectCommand="SELECT LastName FROM Employees">
      </asp:SqlDataSource>

      <asp:ListBox
          id="ListBox1"
          runat="server"
          DataTextField="LastName"
          DataSourceID="SqlDataSource1">
      </asp:ListBox>

    </form>
  </body>
</html>

When the example page is viewed, any view state is stored by the HiddenFieldPageStatePersister class in a <hidden> HTML element named "__VIEWSTATE".

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">  
<HTML>  
  <BODY>  
    <form name="_ctl0" method="post" action="sample.aspx" id="_ctl0">  

      <input type="hidden" name="__VIEWSTATE" value="MgAwADkANgAwADkAOQA3ADgAMQD/AQ8QBQoxMTU2NDc1NjE0EGRkFgICAQ9kFgICAw8PZBAVDQVhc2RhcwhCdWNoYW5hbghDYWxsYWhhbgdEYXZvbGlvCURvZHN3b3J0aAZGdWxsZXIES2luZwhLcmF3YXJpawlMZXZlcmxpbmcETWFyeQdQZWFjb2NrBlN1eWFtYQx0ZXN0IHJlZnJlc2gVDQVhc2RhcwhCdWNoYW5hbghDYWxsYWhhbgdEYXZvbGlvCURvZHN3b3J0aAZGdWxsZXIES2luZwhLcmF3YXJpawlMZXZlcmxpbmcETWFyeQdQZWFjb2NrBlN1eWFtYQx0ZXN0IHJlZnJlc2gUKgMNZ2dnZ2dnZ2dnZ2dnZ2RkZPdhi6U7jBPqVZbj0W8AYFSJ6oiq" />  

      <select size="4" name="ListBox1" id="ListBox1">      
        <option value="Buchanan">Buchanan</option>  
        <option value="Callahan">Callahan</option>  
        <option value="Davolio">Davolio</option>  
        <option value="Dodsworth">Dodsworth</option>  
        <option value="Fuller">Fuller</option>  
        <option value="King">King</option>  
        <option value="Leverling">Leverling</option>  
        <option value="Suyama">Suyama</option>  
      </select>  

    </form>  
  </BODY>  
</HTML>

Remarks

ASP.NET pages can store Page state between the inherently stateless HTTP request and response required to process and serve any Web page. This state is called "view state". The default mechanism used to store view state for a page and its controls is in one or more <hidden> HTML fields included in the page that is served to a client from a Web server. The Page class can use the HiddenFieldPageStatePersister class to do this work. HiddenFieldPageStatePersister implements the Save and Load methods of the PageStatePersister class so that the Page can store state in a <hidden> HTML element named "__VIEWSTATE" on a Web client. When the client requests the same page from the Web server (a postback), the <hidden> element is parsed and converted to state information by ASP.NET.

If the Page instance that is requested has an associated PageAdapter class, it retrieves the PageStatePersister object from this adapter using the GetStatePersister method. Adapters can override the GetStatePersister method to return a PageStatePersister object that stores page and control state in some way that a specific client supports. For example, the SessionPageStatePersister class stores page and controls' state on the Web server, instead of the client, to decrease the amount of information that must be sent and stored on a client that has potentially limited memory and bandwidth.

The maximum size of the "_VIEWSTATE" <hidden> HTML element can be set through the MaxPageStateFieldLength property or through the MaxPageStateFieldLength configuration setting. When this value is set and the length of the "_VIEWSTATE" element would exceed the maximum length, the content is divided into multiple "_VIEWSTATE" elements.

Constructors

HiddenFieldPageStatePersister(Page)

Initializes a new instance of the HiddenFieldPageStatePersister class.

Properties

ControlState	Gets or sets an object that represents the data that controls contained by the current Page object use to persist across HTTP requests to the Web server. (Inherited from PageStatePersister)
Page	Gets or sets the Page object that the view state persistence mechanism is created for. (Inherited from PageStatePersister)
StateFormatter	Gets an IStateFormatter object that is used to serialize and deserialize the state information contained in the ViewState and ControlState properties during calls to the Save() and Load() methods. (Inherited from PageStatePersister)
ViewState	Gets or sets an object that represents the data that controls contained by the current Page object use to persist across HTTP requests to the Web server. (Inherited from PageStatePersister)

Methods

Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
Load()	Deserializes and loads persisted state information from an HttpRequest object when a Page object initializes its control hierarchy.
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
Save()	Serializes any object state contained in the ViewState or ControlState property and writes the state to the response stream.
ToString()	Returns a string that represents the current object. (Inherited from Object)

Applies to

Partilhar via