[RESOLVED] MVVM: Populate a view (with listbox) when an item from another view (with listbox) is

I have a list of Topics, and for each topic there are some Examples. What I want to be able to do is that when a topic is selected then I will populate another view with all Examples for that selected topic. I'm still learning MVVM so not sure how to implement such.

This is what I've got so far but I haven't figured out yet how to receive/set the _exampleViewModel via binding in XAML.

Code:

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public TopicViewModel SelectedTopic
    {
        get { return _selectedTopic; }
        set
        {
            _selectedTopic = value;
            OnPropertyChanged("SelectedTopic");

            //refresh list of exercises
            if (_exampleViewModel != null)
            {
                _exampleViewModel.RefreshExercises(_selectedTopic.ID);
            }
        }
    }

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Why is this question in the VB.NET forum when it's C# code (there's a C# forum) for a WPF application (there's a WPF forum)? I have asked the mods to move it to a more appropriate location. MVVM questions belong in the WPF forum because MVVM is specifically a WPF design pattern.

I've seen some threads here that talked about MVVM so I tried asking here but forgot to convert my code. :D

Quote:

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Originally Posted by dee-u

I've seen some threads here that talked about MVVM so I tried asking here but forgot to convert my code. :D

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It should be in WPF because that's where the people with MVVM experience are. Even if your code was VB, most people who've used MVVM with C# would still be able to answer the question because it's about MVVM and not about VB.NET.

Got it working by exposing a ViewModel to be consumed by the Views. This is my 'parent' ViewModel (stripped unnecessary codes) and as you can see there is the ExerciseVM and Example VM in there:

Code:

---

namespace WorkText.ViewModel
{
    public class AllTopicsViewModel : WorkspaceViewModel
    {
        private TopicViewModel _selectedTopic = null;
        public TopicViewModel SelectedTopic
        {
            get { return _selectedTopic; }
            set
            {
                _selectedTopic = value;

                OnPropertyChanged("SelectedTopic");

                this.ExerciseVM = new AllExercisesViewModel(value);
                this.ExampleVM = new AllExamplesViewModel(value);
            }
        }

        private AllExercisesViewModel _exerciseViewModel = null;
        public AllExercisesViewModel ExerciseVM
        {
            get
            {
                return _exerciseViewModel;
            }
            set
            {
                if (_exerciseViewModel != value)
                {
                    _exerciseViewModel = value;
                    base.OnPropertyChanged("ExerciseVM");
                }
            }
        }

        private AllExamplesViewModel _exampleViewModel = null;
        public AllExamplesViewModel ExampleVM
        {
            get
            {
                return _exampleViewModel;
            }
            set
            {
                if (_exampleViewModel != value)
                {
                    _exampleViewModel = value;
                    base.OnPropertyChanged("ExampleVM");
                }
            }
        }
    }
}

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And this is the ViewModel of Exercises:

Code:

---

namespace WorkText.ViewModel
{
    public class AllExercisesViewModel : ViewModelBase
    {
        public OptimizedObservableCollection<ExerciseViewModel> AllExercises { get; private set; }

        public AllExercisesViewModel(TopicViewModel topic)
        {
            AllExercises = new OptimizedObservableCollection<ExerciseViewModel>();

            _exerciseRepository = new ExerciseRepository();

            List<ExerciseViewModel> all = (from cust in _exerciseRepository.GetExercises(topic.ID)
                                          select new ExerciseViewModel(cust, _exerciseRepository)).ToList();

            AllExercises.AddRange(all);
            this.AllExercises.CollectionChanged += this.OnCollectionChanged;
        }
    }
}

---

And this is how I bind them in XAML.

Code:

---

<Window x:Class="WorkText.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:WorkText"
     
        Title="Worktext" Height="545" Width="926" SnapsToDevicePixels="False" WindowState="Maximized" WindowStyle="SingleBorderWindow" WindowStartupLocation="CenterScreen" Icon="/WorkText;component/Images/Extensions.ico" Closing="Window_Closing" Loaded="Window_Loaded" xmlns:my="clr-namespace:WorkText.View">
       
    <Window.Resources>
        <ResourceDictionary Source="MainWindowResources.xaml" />       
    </Window.Resources>

    <!--Set this window's DataContext to AllTopicViewList so that TopicsView and ExerciseView will be able to bind-->
    <Window.DataContext>
        <Binding Source="{StaticResource TopicList}"/>
    </Window.DataContext>
   
    <Grid>           
                <my:ExamplesView DataContext="{Binding ExampleVM, Mode=OneWay}" HorizontalAlignment="Stretch" x:Name="examplesView" VerticalAlignment="Stretch"  />
                <my:ExercisesView DataContext="{Binding ExerciseVM, Mode=OneWay}" HorizontalAlignment="Stretch" x:Name="exercisesView" VerticalAlignment="Stretch"  />
                    <my:TopicsView Grid.Row="1" Grid.RowSpan="2" HorizontalAlignment="Stretch" x:Name="topicsView" VerticalAlignment="Stretch" />           
        </Grid>
    </Grid>
</Window>

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