Trying to use MVVM to add "ToDoList Task" like item to a StackPanel

it should still fix some issue I have a DataGrid. Right now it's binding to an ObservableCollection in my model just great. ,
That stuff definitely doesn't belong in my model.

I wish this help you When I tap an item, it doesn't seem to register and add a checkmark on the right. When I tap a subsequent item, it shows a checkmark next to the one I tapped previously, but not for the one I just tapped, and so on, always remaining one action behind.

- (void)tableView:(UITableView *)tableView didDeselectRowAtIndexPath:(NSIndexPath *)indexPath

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath

I wish did fix the issue. The 1st is a stateless component, or a function component, that is passed the props and context as params. The 2nd is a class component, and the props are assigned to this.props. See Components and Props in the documentation.
The props are not passed to render() as params. Destructure this.props to your variables.

render() {
    const {todo, todoList, remove} = this.props;
    const status = todo.opened ? 'opened' : 'closed';

    return (
        <li className={"todo " + status} data-endpoint={todo['@id']}>
            <form onChange={this.changeStatus}>
                <a href={window.Routing.generate('todo_list_todo_show', {account: todoList.account.id, list: todoList.id, todo: todo.id}, true)}>{todo.name}</a>
            </form>
        </li>
    );
}

This might help you I'll give you my idea according to what I understood from your question.
MainWindow.xaml.cs

    public partial class MainWindow : Window
{
    private AppleViewModel appleViewModel;
    public AppleViewModel AppleViewModel
    {
        get
        {
            return this.appleViewModel;
        }
        set
        {
            if (this.appleViewModel != value)
            {
                this.appleViewModel = value;
            }
        }
    }

    private BananaViewModel bananaViewModel;
    public BananaViewModel BananaViewModel
    {
        get
        {
            return this.bananaViewModel;
        }
        set
        {
            if (this.bananaViewModel != value)
            {
                this.bananaViewModel = value;
            }
        }
    }


    public MainWindow()
    {
        InitializeComponent();

        this.AppleViewModel = new AppleViewModel();
        this.AppleViewModel.AppleID = "Apple001";
        this.AppleViewModel.Size = 10;

        this.BananaViewModel = new BananaViewModel();
        this.BananaViewModel.BananaID = "Banana001";
        this.BananaViewModel.Length = 10;

        apple.DataContext = this.AppleViewModel;

        banana.DataContext = this.BananaViewModel;

        ObservableCollection<int> sizes = new ObservableCollection<int>();
        for (int i = 0; i < 10; i++)
        {
            sizes.Add(i);
        }

        ListBox.ItemsSource = sizes;

    }

    private void ListBox_OnSelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        if (this.AppleViewModel.IsSelected)
        {
            this.AppleViewModel.Size = (int)ListBox.SelectedItem;
        }
        if (this.BananaViewModel.IsSelected)
        {
            this.BananaViewModel.Length = (int)ListBox.SelectedItem;
        }
    }
}

 <StackPanel Orientation="Vertical">
        <wpfApplication4:AppleControlxaml x:Name="apple"/>
        <wpfApplication4:BananaControl x:Name="banana"/>
        <ListBox SelectionChanged="ListBox_OnSelectionChanged" x:Name="ListBox">
        </ListBox>
    </StackPanel>

private bool isSelected;
    public bool IsSelected
    {
        get
        {
            return this.isSelected;

        }
        set
        {
            this.isSelected = value;
            OnPropertyChanged("IsSelected");
        }
    }

<CheckBox IsChecked="{Binding IsSelected}"/>

private void InitializeSettingsVM(int value, string description)
    {
      //Same like you do when you initialize your Banana/AppleVM in your MainWindow initialize.
      this.SettingsVM.Value = value;
      this.SettingsVM.Description = description;
    }

private void banana1_MouseDown(whateveryouhavehere)
   {
     //Whatever you do here
     this.InitializeSettingsVM(this.BananaViewModel.Length,this.BananaViewModel.BananaID);
   }

wish help you to fix your issue MVVM Light NuGet can only add related resources (assemblies/.cs files) into the project. It wont add Templates into Visual Studio. To get templates in Visual Studio, you have to install MVVM Light Visual Studio Extension by following the below steps.
Open Visual Studio and go to Tools->Extensions and Updates. In the Extensions and Updates window lick Online in the left pane. In the search bar, type MVVM Light. In the search results find MVVM Light for VS2017. Click Download and accept license.