I know this post is 7+ months old at this point, but in case others find their way here, this is how I solved this. I wanted to have a Theater Slide plus the Navigation and I wanted all of the data to come from same source module.
First, I used a standard Widget Template, but I edited the top line to reference a Code Block, and then added a 2nd RadListView to the template with an id of dynamicContentListView2. (Not going to post the RadListView code, but it's the same as the first one, except the markup is different to handle the theater navigation items, rather than the theater slides.)
<%@ Control Language="C#" Inherits="SitefinityWebApp.CustomWidgets.TheaterSlideControl.TheaterSlide" %>
Then I created the TheaterSlide class as follows, and in that class I inherited from a UserControl, grabbed the DataSource from the first RadListView which Sitefinity populates automatically, and added that as the DataSource for my second RadListView.
public class TheaterSlide : System.Web.UI.UserControl
protected override void OnInit(EventArgs e)
RadListView container = (RadListView)this.FindControl("dynamicContentListView");
> detailItems = (List<
RadListView container2 = (RadListView)this.FindControl("dynamicContentListView2");
container2.DataSource = detailItems;
Then I just used standard databinding to bind the elements in the first (theater slides) or second (theater navigation items) RadListView as needed.