How can I access an IFRAME from the codebehind file in ASP.NET?

Question

I am trying to set attributes for an IFRAME html control from the code-behind aspx.cs file.

I came across a post that says you can use FindControl to find the non-asp controls using:

The aspx file contains:

<iframe id="contentPanel1" runat="server" />

and then the code-behind file contains:

protected void Page_Load(object sender, EventArgs e)
{
    HtmlControl contentPanel1 = (HtmlControl)this.FindControl("contentPanel1");
    if (contentPanel1 != null)
     contentPanel1.Attributes["src"] = "http://www.stackoverflow.com";

}

Except that it's not finding the control, contentPanel1 is null.

---

Update 1

Looking at the rendered html:

<iframe id="ctl00_ContentPlaceHolder1_contentPanel1"></iframe>

i tried changing the code-behind to:

HtmlControl contentPanel1 = (HtmlControl)this.FindControl("ctl00_ContentPlaceHolder1_contentPanel1");

if (contentPanel1 != null)
    contentPanel1.Attributes["src"] = "http://www.clis.com";

But it didn't help.

i am using a MasterPage.

---

Update 2

Changing the aspx file to:

<iframe id="contentPanel1" name="contentPanel1" runat="server" />

also didn't help

---

Answer

The answer is obvious, and unworthy of even asking the original question. If you have the aspx code:

<iframe id="contentPanel1" runat="server" />

and want to access the iframe from the code-behind file, you just access it:

this.contentPanel1.Attributes["src"] = "http://www.stackoverflow.com";

Answer 1

Try instantiating contentPanel1 outside the Load event; keep it global to the class.

Answer 2

Try using

this.Master.FindControl("ContentId").FindControl("controlId")

instead.

Answer 3

The FindControl method looks in the child controls of the "control" the method is executed on. Try looking through the control collection recursively.

    protected virtual Control FindControlRecursive(Control root, String id)
    {
        if (root.ID == id) { return root; }
        foreach (Control c in root.Controls)
        {
            Control t = FindControlRecursive(c, id);
            if (t != null)
            {
                return t;
            }
        }
        return null;
    }

Answer 4

If the iframe is directly on the page where the code is running, you should be able to reference it directly:

contentPanel1.Attribute = value;

If not (it's in a child control, or the MasterPage), you'll need a good idea of the hierarchy of the page... Or use the brute-force method of writing a recursive version of FindControl().

Answer 5

Try this.

ContentPlaceHolder cplHolder = (ContentPlaceHolder)this.CurrentMaster.FindControl("contentMain");

HtmlControl cpanel= (HtmlControl)cplHolder.FindControl("contentPanel1");