Page.EnableViewState 属性
定义
获取或设置一个值,该值指示当前页请求结束时该页是否保持其视图状态以及它包含的任何服务器控件的视图状态。Gets or sets a value indicating whether the page maintains its view state, and the view state of any server controls it contains, when the current page request ends.
public:
virtual property bool EnableViewState { bool get(); void set(bool value); };
[System.ComponentModel.Browsable(false)]
public override bool EnableViewState { get; set; }
[<System.ComponentModel.Browsable(false)>]
member this.EnableViewState : bool with get, set
Public Overrides Property EnableViewState As Boolean
属性值
如果该页保持其视图状态,则为 true;否则为 false。true if the page maintains its view state; otherwise, false. 默认值为 true。The default is true.
- 属性
示例
下面的代码示例将 EnableViewState 属性设置为 false 加载页面时的。The following code example sets the EnableViewState property to false when the page is loaded. 这将禁用对象的视图状态 Page ,这意味着页面的视图状态信息和页面中包含的任何控件都不会保存。This disables view state for the Page object, meaning that neither view-state information for the page nor any controls contained by the page are saved.
重要
此示例具有一个接受用户输入的文本框,这是一个潜在的安全威胁。This example has a text box that accepts user input, which is a potential security threat. 默认情况下,ASP.NET 网页验证用户输入是否不包含脚本或 HTML 元素。By default, ASP.NET Web pages validate that user input does not include script or HTML elements. 有关详细信息,请参阅脚本侵入概述。For more information, see Script Exploits Overview.
public class WebPage : Page
{
private MyForm myFormObj;
private Label label1;
private Label label2;
private TextBox textBoxObj;
private Button buttonObj;
public WebPage()
{
Page.Init += new System.EventHandler(Page_Init);
}
private void Page_Load(object sender, System.EventArgs e)
{
// Comment the following line to maintain page view state.
Page.EnableViewState = false;
myFormObj.Method = "post";
Controls.Add(myFormObj);
textBoxObj.Text = "Welcome to .NET";
label1.Text = "Enter a name";
buttonObj.Text = "ClickMe";
buttonObj.Click += new EventHandler(Button_Click);
myFormObj.Controls.Add(label1);
myFormObj.Controls.Add(textBoxObj);
myFormObj.Controls.Add(buttonObj);
myFormObj.Controls.Add(label2);
}
private void Button_Click(object sender, EventArgs e)
{
String temp = "<br>Name is " + textBoxObj.Text + "<br>";
temp += "Saved content of previous page is " + ViewState["name"] as String;
label2.Text = temp;
}
protected override void LoadViewState(object viewState)
{
if(viewState != null)
base.LoadViewState(viewState);
}
protected override object SaveViewState()
{
ViewState["name"] = textBoxObj.Text;
return base.SaveViewState();
}
private void Page_Init(object sender, EventArgs e)
{
this.Load += new System.EventHandler(this.Page_Load);
myFormObj = new MyForm();
label1 = new Label();
label2 = new Label();
textBoxObj = new TextBox();
buttonObj = new Button();
}
};
Public Class WebPage
Inherits System.Web.UI.Page
Private myFormObj As MyForm
Private label1 As Label
Private label2 As Label
Private textBoxObj As TextBox
Private buttonObj As Button
Public Sub New()
AddHandler Page.Init, AddressOf Page_Init
End Sub
Private Sub Page_Load(sender As Object, e As System.EventArgs)
' Comment the following line to maintain page view state.
Page.EnableViewState = false
myFormObj.Method = "post"
Controls.Add(myFormObj)
textBoxObj.Text = "Welcome to .NET"
label1.Text = "Enter a name"
buttonObj.Text = "ClickMe"
AddHandler buttonObj.Click, AddressOf Button_Click
myFormObj.Controls.Add(label1)
myFormObj.Controls.Add(textBoxObj)
myFormObj.Controls.Add(buttonObj)
myFormObj.Controls.Add(label2)
End Sub
Private Sub Button_Click(sender As Object, e As EventArgs)
Dim temp As [String] = "<br>Name is " + textBoxObj.Text + "<br>"
temp += "Saved content of previous page is " + CType(ViewState("name"), String)
label2.Text = temp
End Sub
Protected Overrides Sub LoadViewState(viewState As Object)
If Not (viewState Is Nothing) Then
MyBase.LoadViewState(viewState)
End If
End Sub
Protected Overrides Function SaveViewState() As Object
ViewState("name") = textBoxObj.Text
Return MyBase.SaveViewState()
End Function 'SaveViewState
Private Sub Page_Init(sender As Object, e As EventArgs)
AddHandler Me.Load, AddressOf Me.Page_Load
myFormObj = New MyForm()
label1 = New Label()
label2 = New Label()
textBoxObj = New TextBox()
buttonObj = New Button()
End Sub
End Class
注解
有关为何要禁用视图状态的信息,请参阅 Control.EnableViewState 。For information about why you might want to disable view state, see Control.EnableViewState.
即使 EnableViewState 为 false ,该页也可能包含 ASP.NET 用于检测回发的隐藏视图状态字段。Even if EnableViewState is false, the page might contain a hidden view state field that is used by ASP.NET to detect a postback.