How can I output XML from code behind in an ASPX file?

I need to output XML / ASX on an ASPX page. The XML is generated from the code behind and will look like this.

I'm using string builder to create the XML / ASX.

            (...)
            sb.AppendLine("<asx version='3.0'>");
            sb.AppendLine("<title> Spilliste </title>");
            while (i < pdc.Count)
            {
                sb.AppendLine("<entry>");
                sb.AppendLine("<title>" + pdc[i].PageName + "</title>");
                sb.AppendLine("<abstract> Ikke tilgjengelig</abstract>");
                sb.AppendLine("<ref>" + pdc[i].LinkURL + "</ref>");
                sb.AppendLine("</entry>");
                i++;
            }
            sb.AppendLine("</asx>");

            return sb.ToString();
            (...)

But how can I output this?

Response.Write does not work from code behind. And I'm notable to use <asp:label> in the ASPX file, because it needs to be placed within tags. I basically have a blank ASPX page.

What to do?

Don't use a Page for this. Basically Pages are for rendering html. If you want to send xml or images or any other type of data for that matter you should use a .ashx file and and a class that implements IHttpHandler.

You can see this example on how to implement the interface.