private async Task Search()
 {
     ForumList = new ObservableCollection <ForumListItemViewModel> (RawForumList.FindAll((vm) => {
         return(vm.RoomName.Contains(SearchText));
     }
                                                                                         ));
 }
        private async Task GetForumViewModel(List <ChatRoomDetail> forumList, List <Course> courseList)
        {
            ObservableCollection <ForumListItemViewModel> forumViewModelList = new ObservableCollection <ForumListItemViewModel> ();

            foreach (var course in courseList)
            {
                foreach (ChatRoomDetail item in forumList)
                {
                    if (course.CourseId == item.CourseID)
                    {
                        ForumListItemViewModel vm = new ForumListItemViewModel(item);
                        RawForumList.Add(vm);
                    }
                }
            }
            ForumList = new ObservableCollection <ForumListItemViewModel> (RawForumList);
        }