PreviousPage = null in crosspage posting
<p>I'm trying to pass post data from one page to the next but PreviousPage always equals null.</p>

<p>This is what I have in the original page (inside an updatepanel
)</p>

<pre><code>&lt;asp:Button ID="mmGo" runat="server" Text="Merge" PostBackUrl="~/Default2.aspx?action=merge"/&gt;
</code></pre>

<p>Then in the following page I have:</p>

<pre><code>&lt;%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %&gt;
&lt;%@ PreviousPageType VirtualPath="~/Default.aspx" %&gt;

&lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt;

&lt;html xmlns="http://www.w3.org/1999/xhtml"&gt;
&lt;head runat="server"&gt;
    &lt;title&gt;&lt;/title&gt;
&lt;/head&gt;
&lt;body&gt;
    &lt;form id="form1" runat="server"&gt;

    &lt;div&gt;
        &lt;asp:Label ID="Label1" runat="server" Text="Label"&gt;&lt;/asp:Label&gt;
    &lt;/div&gt;
    &lt;/form&gt;
&lt;/body&gt;
&lt;/html&gt;
</code></pre>

<p>...and in the .cs file:</p>

<pre><code>protected void Page_Load(object sender, EventArgs e)
{
    if (PreviousPage != null)
    {
        string action = Request.QueryString["action"];
        if (action == "merge")
        {
            UpdatePanel SourceControl = (UpdatePanel)PreviousPage.FindControl("UpdatePanel1");
            HiddenField SourceTextBox = (HiddenField)SourceControl.FindControl("txtListIDs");
            if (SourceTextBox != null)
            {
                Label1.Text = SourceTextBox.Value;
            }
        }
    }
    else
    {
        Label1.Text = "page is not cross page post back!";
    }
}
</code></pre>

<p>Any ideas why the PreviousPage is always equal to null?</p>
