Adding to ObservableCollection does not refresh bound view

Question

I have an ObservableCollection bound to a view. Adding to the collection from another ViewModel doesn't change the view after addition. Closing the app and reopening does, though.

Here's the View:

<CollectionView Grid.Row="2" x:Name="ProjectsCollectionView" x:DataType="vm:LandingViewModel"
                ItemsSource="{Binding Projects}"
                SelectionMode="None">
                <CollectionView.ItemTemplate>
                    <DataTemplate>
                    <Frame BorderColor="Black" CornerRadius="10" HasShadow="False" Padding="5">
                        <StackLayout Orientation="Vertical" Padding="5" x:DataType="model:MProject">
                            <Label Text="{Binding projectname}" 
                            LineBreakMode="NoWrap" 
                            Style="{DynamicResource ListItemTextStyle}" 
                            FontSize="16" />
                            <Label Text="{Binding facilityname}" 
                            LineBreakMode="NoWrap"
                            Style="{DynamicResource ListItemDetailTextStyle}"
                            FontSize="13" />
                            <StackLayout.GestureRecognizers>
                                <TapGestureRecognizer 
                                NumberOfTapsRequired="1"
                                Command="{Binding Source={RelativeSource AncestorType={x:Type vm:LandingViewModel}}, Path=ItemTapped}"      
                                CommandParameter="{Binding .}">
                                </TapGestureRecognizer>
                            </StackLayout.GestureRecognizers>
                        </StackLayout>
                    </Frame>
                </DataTemplate>
                </CollectionView.ItemTemplate>
            </CollectionView>

Answer 1

I "solved" it by doing the following: switching the BindingContext declaration from XAML to code behind, and overriding the OnAppearing method to LoadProjects(). I still feel like I'm missing something.

private LandingViewModel _viewModel = new LandingViewModel();
        public LandingPage()
        {
            InitializeComponent();
            BindingContext = _viewModel;
        }

        protected async override void OnAppearing()
        {
            base.OnAppearing();
            _viewModel.LoadProjects();
        }

Answer 2

Here's the ViewModel for that view:

public class LandingViewModel : BaseViewModel
    {
        private static LandingViewModel _instance = new LandingViewModel();
        public static LandingViewModel Instance { get { return _instance; } }
        private MProject _selectedMProject;
        //private ObservableCollection<MProject> _projects;
        public Command<MProject> ProjectTapped { get; }

        public ObservableCollection<MProject> Projects { get; set; }

        public ICommand OpenWebCommand { get; }
        public Command AddProjectCommand { get; set; }
        public LandingViewModel()
        {
            Projects = new ObservableCollection<MProject>();
            Title = "Landing";
            OpenWebCommand = new Command(async () => await Browser.OpenAsync("https://aka.ms/xamarin-quickstart"));
            ProjectTapped = new Command<MProject>(OnProjectSelected);
            AddProjectCommand = new Command(OnAddProject);
            LoadProjects();
        }

        public async void LoadProjects()
        {
            LocalDB localDB = await LocalDB.Instance;
            var list = await localDB.GetProjectsAsync();
            Projects.Clear();
            foreach(var k in list)
            {
                Projects.Add(k);
            }
        }

        public void OnAppearing()
        {
            IsBusy = true;
            SelectedMProject = null;
        }        }

Answer 3

Here's the code from the other viewmodel that adds the new item to the ObservableCollection but doesn't trigger a view refresh:

private async void OnSave()
        {
            MProject newProject = new MProject()
            {
                ///assignments here
            };

            //await DataStore.AddProjectAsync(newProject);
            LocalDB localDB = await LocalDB.Instance;
            await localDB.SaveProjectAsync(newProject,true);
            //LandingViewModel landingViewModel = new LandingViewModel();
            //landingViewModel.Projects.Clear();
            //foreach(var k in await localDB.GetProjectsAsync())
            //{
            //    landingViewModel.Projects.Add(k);
            //}

            LandingViewModel.Instance.Projects.Add(newProject);
            // This will pop the current page off the navigation stack
            await Shell.Current.GoToAsync("..");}

I feel like I'm missing something obvious. Should I create my observablecollection in the BaseViewModel, instead of using the instance variable to access it from the other ViewModel?