View state maintains the state of all asp controls property on the page whenever the page post backs to the web server.
By default, view sate is enabled for every asp control. You can see View state in source view of a page and it is saved in hidden form field on the page. View state is good to maintain but it has also disadvantage that it stuffing too much data into view state and it slow down the process of rendering page.
You can maintain or disable individual control, page or an application.By default EnableViewState="True" for control, page or application.
Disable individual control using Control.EnableViewState property with false.
Use page directive to disable view state on page.
<%@ Page Language="VB" EnableViewState="false" %>
If you set EnableViewState property value false in page directive, then you cannot enable view state property in control level (see the below code)
Code:
Default.aspx
<%@ Page Language="VB" AutoEventWireup="false" EnableViewState="false" CodeFile="Default.aspx.vb" Inherits="_Default" %>
<!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></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Label ID="Label1" runat="server" Text="With View state"></asp:Label>
<asp:Label ID="Label2" runat="server" Text="0"></asp:Label>
<br />
<asp:Label ID="Label3" runat="server" Text="Without View state"></asp:Label>
<asp:Label ID="Label4" runat="server" Text="0" EnableViewState="False"></asp:Label>
<br />
<asp:Label ID="Label5" runat="server" ViewStateMode="Enabled"></asp:Label>
<br />
<asp:Button ID="Button1" runat="server" Text="Click Here !!!!"
onclick="Button1_Click1" />
</div>
</form>
</body>
</html>
Default.aspx.vb
Partial Class _Default
Inherits System.Web.UI.Page
Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load
If Not Page.IsPostBack Then
Label5.Text = "Page is not post back"
Else
Label5.Text = "Page is post back"
End If
End Sub
Protected Sub Button1_Click1(ByVal sender As Object, ByVal e As EventArgs)
Label2.Text = (Int32.Parse(Label2.Text) + 1).ToString()
'EnableViewState at Column level
Label2.EnableViewState = True
Label4.Text = (Int32.Parse(Label4.Text) + 1).ToString()
'EnableViewState at Column level
Label4.EnableViewState = False
End Sub
End Class
Output:
Figure 1
If you set the EnableViewState property value True in page directive, then all control enable its view state property.
<%@ Page Language="VB" AutoEventWireup="false" EnableViewState="true" CodeFile="Default.aspx.vb" Inherits="_Default" %>
Code:
Default.aspx
<%@ Page Language="VB" AutoEventWireup="false" EnableViewState="true" CodeFile="Default.aspx.vb" Inherits="_Default" %>
<!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></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Label ID="Label1" runat="server" Text="With View state"></asp:Label>
<asp:Label ID="Label2" runat="server" Text="0"></asp:Label>
<br />
<asp:Label ID="Label3" runat="server" Text="Without View state"></asp:Label>
<asp:Label ID="Label4" runat="server" Text="0" EnableViewState="False"></asp:Label>
<br />
<asp:Label ID="Label5" runat="server" ViewStateMode="Enabled"></asp:Label>
<br />
<asp:Button ID="Button1" runat="server" Text="Click Here !!!!"
onclick="Button1_Click1" />
</div>
</form>
</body>
</html>
Default.aspx.vb
Partial Class _Default
Inherits System.Web.UI.Page
Protected Sub Page_Load(sender As Object, e As System.EventArgs) Handles Me.Load
If Not Page.IsPostBack Then
Label5.Text = "Page is not post back"
Else
Label5.Text = "Page is post back"
End If
End Sub
Protected Sub Button1_Click1(ByVal sender As Object, ByVal e As EventArgs)
Label2.Text = (Int32.Parse(Label2.Text) + 1).ToString()
'EnableViewState at Column level
Label2.EnableViewState = True
Label4.Text = (Int32.Parse(Label4.Text) + 1).ToString()
'EnableViewState at Column level
Label4.EnableViewState = False
End Sub
End Class
Output:
Figure 2
Disable or Enable view state using web configuration file.
You can disable application by setting the <pages EnableViewState="False"/> in web.config file.
web.config
<?xml version="1.0"?>
<configuration>
<system.web>
<pages enableViewState="false"/>
<compilation debug="true" strict="false" explicit="true" targetFramework="4.0"/>
</system.web>
</configuration>
Output:
Figure 3
Web.config
<?xml version="1.0"?>
<configuration>
<system.web>
<pages enableViewState="true"/>
<compilation debug="true" strict="false" explicit="true" targetFramework="4.0"/>
</system.web>
</configuration>
Output:
Figure 4