Manages the view state of ASP.NET server controls, including pages. This class cannot be inherited.

For a list of all members of this type, see StateBag Members.

System.Object
   System.Web.UI.StateBag

[Visual Basic]
NotInheritable Public Class StateBag
   Implements IStateManager, IDictionary, ICollection, IEnumerable
[C#]
public sealed class StateBag : IStateManager, IDictionary,
   ICollection, IEnumerable
[C++]
public __gc __sealed class StateBag : public IStateManager,
   IDictionary, ICollection, IEnumerable
[JScript]
public class StateBag implements IStateManager, IDictionary,
   ICollection, IEnumerable

Thread Safety

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Remarks

View state for a page or control is the cumulative propery values, or view, of that page or control. You can access this class through the Control.ViewState property.

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 save the changes to the page's or control's view state.

You can read from this class during any stage of the control processing lifecycle, but you should not write to it while the control is rendering.

This class implements a dictionary, and you can add or remove items from it as you would any dictionary object. For more information about data collections, such as dictionaries, see Grouping Data in Collections.

Example

The following 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.

[Visual Basic] 
' 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 LabelVB : Inherits Control

       ' Add property values to view state with set; 
       ' retrieve them from view state with get.
       Public Property [Text] As String
          Get
              Return CStr(ViewState("Text"))
          End Get
          Set
              ViewState("Text") = Value
          End Set
       End Property


       Public Property FontSize As Integer
          Get
              Return CInt(ViewState("FontSize"))
          End Get
          Set 
              ViewState("FontSize") = Value
          End Set 
       End Property
       <System.Security.Permissions.PermissionSetAttribute(System.Security.Permissions.SecurityAction.Demand, Name:="FullTrust")> _
       Protected Overrides Sub Render(Output As HtmlTextWriter)
           Output.Write("<font size=" & Me.FontSize & ">" & Me.Text & "</font>")
       End Sub

    End Class

End Namespace

[C#] 
// This control renders values stored in view state for Text and FontSize properties.
using System;
using System.Web;
using System.Web.UI;

namespace ViewStateControlSamples {

    public class Label: Control {


       // Add property values to view state with set;
       // retrieve them from view state with get.
       public String Text {
          get {
              return (String) ViewState["Text"];
          }
          set {
              ViewState["Text"] = value;
          }
       }


       public int FontSize {
          get {
              return (int) ViewState["FontSize"];
          }
          set {
              ViewState["FontSize"] = value;
          }
       }
 
       [System.Security.Permissions.PermissionSet(System.Security.Permissions.SecurityAction.Demand, Name="FullTrust")]
       protected override void Render(HtmlTextWriter output) {
           output.Write("<font size=" + this.FontSize + ">" + this.Text + "</font>");
       }
    }    
}

[C++] 
// This control renders values stored in view state for Text and FontSize properties.
#using <mscorlib.dll>
#using <System.dll>
#using <System.Web.dll>
using namespace System;
using namespace System::Web;
using namespace System::Web::UI;

public __gc class Label : public Control 
{
   // Add property values to view state with set;
   // retrieve them from view state with get.
public:
   __property String * get_Text()
   {
      return dynamic_cast<String*>(ViewState->Item[S"Text"]);
   }

   __property void set_Text(String * value)
   {
      ViewState->Item[S"Text"] = value;
   }

   __property int get_FontSize()
   {
      return *dynamic_cast<__box int*>(ViewState->Item[S"FontSize"]);
   }

   __property void set_FontSize(int value) 
   {
      ViewState->Item[S"FontSize"] = __box(value);
   }

protected:
   [System::Security::Permissions::PermissionSet(System::Security::Permissions::SecurityAction::Demand, Name="FullTrust")]
   void Render(HtmlTextWriter * output)
   {
      output->Write(S"<font size= {0} {1} </font>", __box(this->FontSize), this->Text);
   }
};

[JScript] 

Requirements

Namespace: System.Web.UI

Platforms: Windows 2000, Windows XP Professional, Windows Server 2003 family

Assembly: System.Web (in System.Web.dll)

See Also

StateBag Members | System.Web.UI Namespace | IStateManager | IDictionary | ViewState | Introduction to Web Forms State Management | Grouping Data in Collections | System.Web.UI.AttributeCollection