Attach commands to TreeView in wpf using prism

Question

How do I use a DelegateCommand in a TreeView to get the Expanded event?

Should I be using the DelegateCommand or is there another way?

Thanks

Answer 1

Since you are mentioning Prism, I assume you have a controller or ViewModel attached to the view containing your TreeView...

That being the case, expose a boolean property IsExpanded

    private bool _isExpanded;
    public bool IsExpanded
    {
        get { return _isExpanded; }
        set
        {
            if (value != _isExpanded)
            {
                _isExpanded = value;
                RaisePropertyChanged("IsExpanded");
                //  Apply custom logic here...
            }
        }
    }

Now to hook this property up to the TreeView, you need to apply the following style in the TreeView's resources (or further up the Visual tree as appropriate)

<Style TargetType="{x:Type TreeViewItem}">
    <Setter Property="IsExpanded" Value="{Binding Path=IsExpanded, Mode=TwoWay}" />
</Style>

NB: You can also use a similar technique to hook up the IsSelected property - also very useful!!