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Control.SaveViewState Method

Saves any server control view-state changes that have occurred since the time the page was posted back to the server.

Namespace: System.Web.UI
Assembly: System.Web (in system.web.dll)
protected virtual Object SaveViewState ()
protected Object SaveViewState ()
protected function SaveViewState () : Object
Not applicable.

Return Value

Returns the server control's current view state. If there is no view state associated with the control, this method returns a null reference (Nothing in Visual Basic).

View state is the accumulation of the values of a server control's properties. These values are automatically placed in the server control's ViewState property, which is an instance of the StateBag class. This property's value is then persisted to a string object after the save state stage of the server control life cycle. For more information, see Introduction to the ASP.NET Page Life Cycle.

When view state is saved, this string object is returned to the client as a variable that is stored in an HTML HIDDEN element. When you author a custom server control with a custom view state, the view state can be managed explicitly with the SaveViewState and LoadViewState methods. For more information, see ASP.NET State Management. For information on implementing a custom session-state provider, see Implementing a Session-State Store Provider.

The following example overrides the SaveViewState method in a custom ASP.NET server control. When this method is invoked, it determines whether the control has any child controls and whether the containing Page object is the result of a postback. If both are true, it changes the Text property of a Label Web server control to read Custom Control Has Saved State. It then saves the view state of the control as an array of objects, named allStates.

protected override object SaveViewState()
{  // Change Text Property of Label when this function is invoked.
   if(HasControls() && (Page.IsPostBack))
   {
      ((Label)(Controls[0])).Text = "Custom Control Has Saved State";
   }
   // Save State as a cumulative array of objects.
   object baseState = base.SaveViewState();
   string userText = UserText;
   string passwordText = PasswordText;
   object[] allStates = new object[3];
   allStates[0] = baseState;
   allStates[1] = userText;
   allStates[2] = PasswordText;
   return allStates;
}

protected Object SaveViewState()
{
    // Change Text Property of Label when this function is invoked.
    if (HasControls() && get_Page().get_IsPostBack()) {
        ((Label)(get_Controls().get_Item(0))).set_Text(
            "Custom Control Has Saved State");
    }

    // Save State as a cumulative array of objects.
    Object baseState = super.SaveViewState();
    String userText = get_UserText();
    String passwordText = get_PasswordText();
    Object allStates[] = new Object[3];
    allStates.set_Item(0, baseState);
    allStates.set_Item(1, userText);
    allStates.set_Item(2, get_PasswordText());
    return allStates;
} //SaveViewState

Windows 98, Windows Server 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0
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