Hi,
EDIT: The issue underneath is fixed, GO TO EDIT2 in this post.
I have an Organisation entity and a Region entity. An object of type Organisation can have one or more Region objects connected to it, thus I have a foreign key in my Region entity to the Organisation Entity. The Organisation and Region objects are pulled from my database using WCF RIA and entity framework. I want to put the Organisation objects in one ComboBox and the Region objects in another ComboBox, and when selecting an organsation having the ComboBox for Region objects automatically only showing regions that are connected to the selected organisation. Should be pretty basic, but the way I've designed it right now it doesnt work at all.
So, any hint to how I can achive this? A simple simple codeexample is much appreciated! (I'm using SL4,WCF RIA MVVM)
EDIT2 EDIT2 EDIT2 EDIT2 EDIT2 EDIT2 EDIT2 EDIT2 EDIT2 EDIT2 EDIT2 EDIT2:
Using Venomo's ElemntBinding answer this is working great for me now when I want to add a new object to my collection, and I'm just pulling the avaible countries and connected regions and then type a site in a textbox...So I get my combination of Organisation, region and site in my database :)
Now, I've got a new problem when I want to EDIT a site in my collection. In EDIT mode, I want the two dropdowns to be preselected and disabled (BusinessRule is that I can edit the sitename, not which organisation og region it's connected to). So by setting the SelectedIndex property on Organisation combobox I get my organisation selected, but when doing the same on the Regions combobox it fails with an Object Reference error.