Question

We have a screen and its view model:

public class ScreenViewModel : BaseViewModel
{
    [NotifyPropertyChanged]
    public List<Node> Nodes { get; set; }

    public ICommand NodeClickedCommand { get; set; }

    public ScreenViewModel()
    {
        NodeClickedCommand = new RelayCommand(NodeClicked);
        // ....
        // Some code that binds Nodes.
        // ....
    }

    private void NodeClicked()
    {
        MessageBox.Show("This is never shown");
    }
}

On this page we have custom control (CustomControl) and following xaml to bind the command:

<UserControl x:Class="ScreenView"
    x:Name="Screen"
    >
     <CustomControl Nodes="{Binding Nodes}">
                <CustomControl.ItemTemplate>
                    <DataTemplate>
                                <Button Command="{Binding ElementName=Screen,
                                     Path=DataContext.NodeClickedCommand}">
                                    <TextBlock>hello</TextBlock>
                                </Button>
                    </DataTemplate>
                </CustomControl.ItemTemplate>
        </CustomControl>

Our custom SL control uses the above template (DataTemplate) to display it’s children:

foreach(Node node in Nodes)
{
    FrameworkElement frameworkElement = (FrameworkElement)ItemTemplate.LoadContent();
    frameworkElement.DataContext = node ;
    this._canvas.Children.Add(frameworkElement);
}

We are sure that:

• ViewModel is correctly bound to View
• All nodes are displayed correctly
• Regular binding works correctly
• There are no binding warnings in VS
• Command binding works if we bind with Command=”{Binding NodeClickedCommand}”, but of course this binds to command that should exist on single node and we want to bind to command that exists on the screen view model.
• Simmilar scenario works with ListBox and ListBox.ItemTemplate

The problem is that NodeClickedCommand is never bound, why?

Answer 1

It seems that using ContentPresenter instead of ItemTemplate.LoadContent solves this issue:

foreach(Node node in Nodes)
{
    ContentPresenter contentPresenter = new ContentPresenter();
    contentPresenter.Content = node;
    contentPresenter.ContentTemplate = ItemTemplate;
    this._canvas.Children.Add(contentPresenter);

//    FrameworkElement frameworkElement = (FrameworkElement)ItemTemplate.LoadContent();
//    frameworkElement.DataContext = node ;
//    this._canvas.Children.Add(frameworkElement);
}

Thanks to dain as he pointed me to the right direction.