ListView doesn't Filter after adding new Item to the list.

I'm creating an application that consists of multiple filters and a ListView which displays data from an Entity Framework database. 

Within my application, I get a strange behavior that occurs within my listview when I add a new item to a list.

When I first load my application, I am able to filter through the list of items that is presented within the `listview` with no problems. However, when Iadd an item to this list, the filter doesn't work at all.

Within my view, I bind my listview the an ObservableCollection which is within a class called CourseListViewModel, like so;

<ListView ... ItemsSource="{Binding CourseList}">

    private ObservableCollection<CourseViewModel> courseList = null;
    public ObservableCollection<CourseViewModel> CourseList
    {
        get { return courseList; }
        set
        {
             courseList = value;
             OnPropertyChanged("CourseList");
        }
    }

And, within my constructor, I have done something like so;

     public CourseListViewModel()
        {
            CourseList = new ObservableCollection<CourseViewModel>(GetCourse());
            CollectionViewSource.GetDefaultView(CourseList).Filter = new Predicate<object>(MainFilter);
        }

Due to the use of the `singleton pattern`, I add an item within the `CourseViewModel` like so;

public CourseListViewModel Course
        {
            get { return CourseListViewModel.Instance(); }
        }

    private void Update()
        {
            if (this.Mode == Mode.Add)
            {
                courserep.AddCourse(this); //courserep is referring to my repository which adds a course to the EF database
                MessageBox.Show("A course has been added successfully.");

                this.Course.CourseList = this.Course.GetCourse();
            }

As you can see, I use this.Course.CourseList = this.Course.GetCourse(); to update my listview when a new entry has been added.

However, I think that is where my issue lies. Therefore, I was wondering if there was an alternative way to update the listview when a new entry has been added. I have put together a sample of the whole problem whichcan be found here. Any help or guidance is very much appreciated. Thanks in advance.