 <p>It's actually doing exactly what it should. <a href="http://msdn.microsoft.com/en-us/library/yw97w238.aspx" rel="nofollow"><code>Server.Execute()</code></a> basically will insert the second page's content into the first page, including ViewState.</p> <p>To remedy your problem, are you able to disable ViewState on the page that's being called (demo.aspx)?</p> <pre><code>&lt;%@ Page Language="C#" EnableViewState="false" CodeBehind="demo.aspx.cs" </code></pre>