Screencast: how to enable server-side history management in an ASP.NET Ajax application

I've recently recorded a screencast showing how to enable server-side history management (in other words, handling the back button) in an ASP.NET Ajax application. The whole video is less than 15 minutes total and I build the whole application from scratch in there (in VB).

I hope it shows just how simple history management is made by ASP.NET Ajax and that it helps understanding the state model that it's built on.

The same video in a variety of formats and in a resolution where the code is actually readable can be found here:
http://www.asp.net/downloads/3.5-extensions/

For those people who find it difficult to cut and paste code from a video by doing a screen capture and then using OCR over it, here's the source code of the mini-app that's being built in the video:

Default.aspx:

<asp:ScriptManager ID="ScriptManager1" runat="server" 
    EnableHistory="True" EnableStateHash="False"/>

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
        <asp:Wizard ID="Wizard1" runat="server">
            <WizardSteps>
                <asp:WizardStep runat="server" Title="Step 1">
                    <asp:TextBox ID="TextBox1" runat="server"/>
                </asp:WizardStep>
                <asp:WizardStep runat="server" Title="Step 2">
                    <asp:TextBox ID="TextBox2" runat="server"/>
                </asp:WizardStep>
                <asp:WizardStep runat="server" Title="Step 3">
                    <asp:TextBox ID="TextBox3" runat="server"/>
                </asp:WizardStep>
            </WizardSteps>
        </asp:Wizard>
    </ContentTemplate>
</asp:UpdatePanel>

Default.aspx.vb:

Partial Class _Default
    Inherits System.Web.UI.Page

    Protected Sub Wizard1_ActiveStepChanged(_
        ByVal sender As Object, ByVal e As System.EventArgs) _
        Handles Wizard1.ActiveStepChanged

        If ScriptManager1.IsInAsyncPostBack And _
           Not ScriptManager1.IsNavigating Then

            ScriptManager1.AddHistoryPoint("index", _
                Wizard1.ActiveStepIndex, _
                "Wizard step " & Wizard1.ActiveStepIndex)
        End If
    End Sub

    Protected Sub ScriptManager1_Navigate(_
        ByVal sender As Object, ByVal e As HistoryEventArgs) _
        Handles ScriptManager1.Navigate

        Dim indexString As String = e.State("index")
        If String.IsNullOrEmpty(indexString) Then
            Wizard1.ActiveStepIndex = 0
        Else
            Dim index As Integer = Convert.ToInt32(indexString)
            Wizard1.ActiveStepIndex = index
        End If
        Page.Title = "Wizard step " & indexString
    End Sub
End Class

http://www.asp.net/downloads/3.5-extensions/