Asynchrously display a list in WPF

I have a WPF application in .net 4.5. This app initiates long running tasks. Each task creates a list of items that needs to be displayed asynchrously. The list of item needs to be dsiplayed in a datagrid.
I was able to this with a classic winforms app but not in WPF.
I have an sync task that runs in the background with a delegate that displays to a windows form user control. It worked great in classic windows forms but not in WPF.

Do you have any good ideas?

Certified Geek