Need debugging hints: Visibility change on Postback works on one page but not another

I have a webform containing a user control. On that user control is a set of radio buttons. When the radio button is changed, a panel and a text box is shown or hidden depending on which radio button was selected.

I can give you an example that works correctly:

testcontrol.aspx:

<asp:RadioButtonList ID="ChoicesRadioButtonList" AutoPostBack="true" OnSelectedIndexChanged="ChoicesRadioButtonList_SelectedIndexChanged" runat="server">
    <asp:ListItem Text="Show 1"></asp:ListItem>
    <asp:ListItem Text="Show 2"></asp:ListItem>
</asp:RadioButtonList>
<asp:Panel id="Panel1" CssClass="panel1" runat="server"></asp:Panel>
<asp:Panel id="Panel2" CssClass="panel2" runat="server"></asp:Panel>

testcontrol.aspx.cs:

protected void ChoicesRadioButtonList_SelectedIndexChanged(object sender, EventArgs e)
{
    RadioButtonList bob = (RadioButtonList)sender;
    switch (bob.SelectedValue)
    {
        case "Show 1":
            Panel1.Visible = true;
            Panel2.Visible = false;
            break;
        case "Show 2开发者_如何学Python":
            Panel1.Visible = false;
            Panel2.Visible = true;
            break;
    }
}

As I mentioned, in a test form this works properly. Panel1 and Panel2 are displayed correctly based on which radio button is selected.

I have another web page and user control with a number of other fields. When this code is on that page, I can step through the code behind for the ChoicesRadioButtonList_SelectedIndexChanged event, but nothing happens.

I am at a loss for next steps to debug this (short of rebuilding the entire page from scratch). Can anyone offer any suggestions on where to look?

Have you tried using an asp:MultiView instead of asp:Panel?

Then instead of switching the visibility of multiple panels, you just need to use SetActiveView(view) to show the required view.

Can you write the same code at PreRender event? Maybe something is changing the visiblity back to the default state and you are overlooking it.

I went through and started commenting out sections of code. Turns out a CalendarExtender on the page was causing the problem. It was throwing javascript errors that prevented the page from rendering corretly.