c# - UI not updating after binding the ItemsSource -

i binding itemssource observablecollection code below

services.restservices.getnotifications(userid, ++page).continuewith((task) =>         {             dispatcher.begininvoke((action)(() =>               {                 setnotlisttobind(task.result).continuewith(t =>                   {                       dispatcher.begininvoke((action)(() =>                            {                             var list = getfilterednotlist(notlist, notificationcategories.requests);                             dispatcher.begininvoke(() => notificationcontainer.itemssource = list;);                            }));                   });               }));         }); 

in above code using task-parallel-library wait excecution , within binding itemssource dispature, ui not updating after binding.
here itemssource notificationcontainer , observablecollection list

if know services.restservices.getnotifications being called ui thread, simplify code specifying taskscheduler instance on each call continuewith using taskscheduler.fromcurrentsyncronizationcontext. perhaps can lead closer finding issue.