Error CS1601 from ASP.NET Application, but can't see why
<p>I'm working my way through this tutorial <a href="http://www.aspnettutorials.com/tutorials/themes/progress-bar-csharp.aspx" rel="nofollow">here</a> about progress dialogues but have hit an elementary problem I can't see the cause of. The my project so far returns the error message...</p>

<pre><code>Compiler Error Message: CS1061: 'ASP.webprogressbar_aspx' does not contain a
definition for 'Button1_Click' and no extension method 'Button1_Click' accepting
a first argument of type 'ASP.webprogressbar_aspx' could be found (are you
missing a using directive or an assembly reference?)

Source Error:

Line 12:     &lt;legend&gt;WebProgressBar&lt;/legend&gt;
Line 13:     &lt;div&gt;
Line 14:       &lt;asp:Button id="Button1"
Line 15:                   runat="server"
Line 16:                   Text="Start Long Task!"
</code></pre>

<p>The project so far is (in its entirety), the WebProgressBar.aspx</p>

<pre><code>&lt;%@ Page Language="C#"
         AutoEventWireup="true"
         CodeBehind="WebProgressBar.aspx.cs"%&gt;
&lt;html&gt;
&lt;head id="Head1" runat="server"&gt;
&lt;title&gt; &lt;/title&gt;
&lt;/head&gt;
&lt;body&gt;
&lt;form id="form1" runat="server"&gt;
  &lt;fieldset&gt;
   &lt;legend&gt;WebProgressBar&lt;/legend&gt;
    &lt;div&gt;
      &lt;asp:Button id="Button1"
                  runat="server"
                  Text="Start Long Task!"
                  OnClick="Button1_Click"&gt;
      &lt;/asp:Button&gt;
    &lt;/div&gt;
  &lt;/fieldset&gt;
&lt;/form&gt;
&lt;/body&gt;
&lt;/html&gt;
</code></pre>

<p>and the WebProgressBar.aspx.cs...</p>

<pre><code>using System;

public partial class WebProgressBar : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }

    public void Button1_Click(object sender, EventArgs e)
    {
        Session["State"] = 1;
    }

}
</code></pre>

<p>Can anyone see what I have overlooked?</p>
