Manages the view state of ASP.NET server controls, including pages. This class cannot be inherited.
Assembly: System.Web (in System.Web.dll)
View state for a page or control is the cumulative property values, or view, of that page or control. You can access this class through the Control.ViewState property. Controls can also store essential state information in control state, but that information is not stored as a object.
This class is the primary storage mechanism for all HTML and Web server controls. It stores attribute/value pairs as strings associated with the control. It tracks changes to these attributes only after the OnInit method is executed for a page request, and saves the changes to the page's or control's view state.
This class implements a dictionary, and you can add items to it or remove items from it as you would any dictionary object. For more information about data collections, such as dictionaries, see Collections and Data Structures.
The following code example demonstrates a composite Label control that has Text and FontSize properties. These properties are saved to and retrieved from view state when the Control.Render method is called on the control.
' This control renders values stored in view state for Text and FontSize properties. Imports System Imports System.Web Imports System.Web.UI Namespace ViewStateControlSamples Public Class CustomLabel : Inherits Control Private Const defaultFontSize As Integer = 3 ' Add property values to view state with set; ' retrieve them from view state with get. Public Property [Text]() As String Get Dim o As Object = ViewState("Text") If (IsNothing(o)) Then Return String.Empty Else Return CStr(o) End If End Get Set(ByVal value As String) ViewState("Text") = value End Set End Property Public Property FontSize() As Integer Get Dim o As Object = ViewState("FontSize") If (IsNothing(o)) Then Return defaultFontSize Else Return CInt(ViewState("FontSize")) End If End Get Set(ByVal value As Integer) ViewState("FontSize") = value End Set End Property <System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _ Protected Overrides Sub Render(ByVal Output As HtmlTextWriter) Output.Write("<font size=" & Me.FontSize & ">" & Me.Text & "</font>") End Sub End Class End Namespace
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98
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.