View State

Introduction#

View State is the method to preserve the Value of the Page and Controls between round trips. It is a Page-Level State Management technique. View State is turned on by default and normally serializes the data in every control on the page regardless of whether it is actually used during a post-back.

Syntax#

ViewState[“NameofViewstate”] = “Value”;

Example

ASPX

<%@ Page Language="C#" AutoEventWireup="true"  CodeFile="Default.aspx.cs" Inherits="_Default" %>
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
    <html xmlns="https://www.w3.org/1999/xhtml" >
    <head runat="server">
        <title>ViewState</title>
    </head>
    <body>
        <form id="form1" runat="server">
            <asp:TextBox runat="server" id="NameField" />
            <asp:Button runat="server" id="SubmitForm" onclick="SubmitForm_Click" text="Submit & set name" />
            <asp:Button runat="server" id="RefreshPage" text="Just submit" />
            <br /><br />
            Name retrieved from ViewState: <asp:Label runat="server" id="NameLabel" />
        </form> 
    </body>
    </html>

Code behind

using System;
using System.Data;
using System.Web;

public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if(ViewState["NameOfUser"] != null)
            NameLabel.Text = ViewState["NameOfUser"].ToString();
        else
            NameLabel.Text = "Not set yet...";
    }

    protected void SubmitForm_Click(object sender, EventArgs e)
    {
        ViewState["NameOfUser"] = NameField.Text;
        NameLabel.Text = NameField.Text;
    }
}