Question

I’m using Microsoft Visual Web Developer 2010 Express.

I have a hidden image button, that is set to visible="true" if the user uploads an image.
Here is the code:

aspx file:

           <asp:UpdatePanel ID="upOne" runat="server" UpdateMode="Conditional">
                <ContentTemplate>
                    <asp:ImageButton ID="btnImageOne" runat="server" CssClass="btnImage" 
                        Visible="false" onclick="btnImageOne_Click" />
                    <asp:LinkButton ID="btnDeleteOne" runat="server" CssClass="btnDelete" Visible="false"
                        onclick="btnDeleteOne_Click">&nbsp;</asp:LinkButton>
                </ContentTemplate>
            </asp:UpdatePanel>

When visible, if clicked by the user, the button does:
aspx.cs file:

    protected void btnDeleteOne_Click(object sender, EventArgs e)
    {
        if (Session["fuOneFilename"] != null)
        {
            File.Delete(Server.MapPath("~/animals/temp/") + (string)Session["fuOneFilename"]);
            Session["fuOneFilename"] = null;
            DisplayUploadedPictures();

            if (Session["mainImageFilename"] == Session["fuOneFilename"])
            {
                Session["mainImageFilename"] = null;
                DisplayMainImage();
            }
        }
    }

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I placed a Break Point in the seccond line of the aspx.cs file.
After pressing F5, the application stops in a JavaScript line, located inside the jQuery (unmodified) file.

j = Array.prototype.push

I am presented with the message:

Runtime Error in Microsoft JScript: ‘Array’ is not defined

In the same window, I can see three buttons:
Break, Continue, Ignore.

Note: Break Points in the Page Load run without a problem.

---

The call stack says:

Anonymous Function JScript

JScript global code JScript

---

Questions:

Q1. Why is this happening?

Q2. How can I fix it?

Answer 1

Q1. Why is this happening?

This error happens if you have the following configuration:

<collapsible panel>
    <iframe>
        <script>
        </script>
    </iframe>
</collapsible panel>

When the page loads, the panel being shown forces the script inside the iframe to be dragged through the DOM before the javascript libraries are loaded.

---

Q2. How can I fix it?

The solution is to declare the source attribute through jQuery:

open: function(){
    document.getElementById("iframename").src = "page.aspx";
}

---

Final Notes:

All credits of this answer go to spender, who pointed me in the right direction with his comment.

However, I didnt want to leave this question “unanswered”, so I decided to gather the info from the linked post and assemble it into a single post.