I'm need of some help trying to understand why I'm getting the above error. not that it needs to be said, but I'm .NET noob.

I've got a usercontrol that requires a URL to work. the usercontrol is

Code:
<cc1:rssdatasource id="RssDataSource2"  runat="server" url="" MaxItems="5" ></cc1:rssdatasource>
In my code behind page I've got this

Code:
public partial class AgentDetail : System.Web.UI.Page
{
    public string feedURL = "";

protected void Page_Load(object sender, EventArgs e)
    {
        if (CmsContext.Current.Document.SiteMarker == "Name")
        {
            feedURL = "/syndication.axd?category=79277ca4-d8bb-4bc8-83c5-022821a8a8a4";
        }
        else
        {
            feedURL = "test";//just an example
        }
      RssDataSource2.url = feedURL;
    }
}
So what I'm trying to do is grab the value of the SiteMarker and input it into the usercontrol's URL 'property' with the feedURL variable. The variable is returning the value correctly but when I load the page I get a compilation error:

CS0117: 'RssToolkit.RssDataSource' does not contain a definition for 'url'

I've got no idea how to decipher that and I've been searching and trying things for literally hours. I'm using this same usercontrol on another page with the url manually entered and it works fine. It also works fine on this page if I manually add the url to the url property like


Code:
<cc1:rssdatasource id="RssDataSource2"  runat="server" url="/syndication.axd?category=79277ca4-d8bb-4bc8-83c5-022821a8a8a4" MaxItems="5" ></cc1:rssdatasource>
NOTE: I've removed the full URL from this code but not in my actual code

Does anyone know what I'm missing here?