Use ViewState to create a simple counter (C#) : ViewState « Page Lifecycle « ASP.NET Tutorial

File: Default.aspx

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="SimpleCounter" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
        <asp:Button ID="cmdIncrement" 
                    runat="server" 
                    OnClick="cmdIncrement_Click" 
                    Text="Increment" /><br />
        <br />
        <asp:Label ID="lblCount" runat="server"></asp:Label>&nbsp;</div>
    </form>
</body>
</html>


File: Default.aspx.cs

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class SimpleCounter : System.Web.UI.Page
{
  protected void cmdIncrement_Click(object sender, EventArgs e)
  {
        int counter;
        if (ViewState["Counter"] == null)
        {
            counter = 1;
        }
        else
        {
            counter = (int)ViewState["Counter"] + 1;
        }

        ViewState["Counter"] = counter;
        lblCount.Text = "Counter: " + counter.ToString();
  }
}

5.21.ViewState
	5.21.1.	Use ViewState to create a simple counter (C#)
	5.21.2.	Save string variable to ViewState
	5.21.3.	Convert.FromBase64String and view state encoding
	5.21.4.	Use ViewState to store random data
	5.21.5.	Visualize the current Base64-encoded contents of the view state
	5.21.6.	Track Your Viewstate