Data Binding within Data Context

Question

I'm a bit new to data-binding and had a question about how to properly access "child" objects within the data context. In my code currently I have a simple view model object:

class MyViewModel
{
    public Dictionary<int, string> seriesChoices = new Dictionary<int, string>();
    ...
}

In the Main Window, if I set the data context of the view to the dictionary directly, I am able to get data-binding to work:

ViewModel selectValues = new ViewModel(); 
MyView.DataContext = selectValues.seriesChoices;

....(relevant XAML)

<ComboBox x:Name="ComboBox1" 
              ItemsSource="{Binding}"
              SelectedValuePath="Key"
              DisplayMemberPath="Value"
              />

What I would like to do is set the DataContext to the ViewModel object directly, and then specify underlying objects, but I can't seem to get this to work. This is the most recent thing I have tried:

MyView.DataContext = selectValues

....(relevant XAML)

<ComboBox x:Name="ComboBox1" 
          ItemsSource="{Binding seriesChoices}"
          SelectedValuePath="Key"
          DisplayMemberPath="Value"
          />

Answer 1

Bindings only work on properties, so change your seriesChoices member into a property and see if that works.

class MyViewModel
{
    private Dictionary<int, string> _seriesChoices = new Dictionary<int, string>();

    public Dictionary<int, string> seriesChoices { get { return _seriesChoices; } }

    ...
}

Note that if you use a getter only, you may have to add Mode=OneWay to the binding in XAML.

Also note that if you want your UI to respond to changes in the dictionary, that is a whole other can of worms, see ObservableCollection<> and INotifyPropertyChanged