Retrieving bound object on node from TreeView

Question

I'm not an expert in WPF so forgive me if I am wording my question weirdly. I'd be more than happy to elaborate if anything doesn't make sense.

I have a treeview that binds an observablecollection of a class. When my program launches, I read every C sourcecode files at a particular destination, store its name and filepath in the class mentioned.

Here is my XAML:

<TreeView Name="ProgramTree" ItemsSource="{Binding ProgramItemCollection}" 
                                      cal:Message.Attach="[Event PreviewMouseRightButtonDown] = [Action TestRight($dataContext,$eventArgs)];
                                      [Event PreviewMouseDoubleClick] = [Action NodeDoubleClick($dataContext,$eventArgs)]">

    <TreeView.Resources>
        <!--DataTemplate for Program Nodes (Top) and binds FileItemNodes-->
        <HierarchicalDataTemplate DataType="{x:Type my:ProgramItem}"
                                        ItemsSource="{Binding FileItemCollection}">
            <Border Width="100" BorderBrush="RoyalBlue" 
                                            Background="RoyalBlue"  BorderThickness="1" 
                                            CornerRadius="2" Margin="2" Padding="2" >
                <StackPanel Orientation="Horizontal">
                    <Image Style="{StaticResource IconStyle}" Margin="2" Source="{StaticResource FolderIcon}" />
                    <TextBlock Margin="2" Text="{Binding ProgramName}"
                                                           Foreground="White" FontWeight="Bold"/>
                </StackPanel>
            </Border>
        </HierarchicalDataTemplate>
        <!--DataTemplate for File Nodes (Subnodes of Program Nodes)-->
        <HierarchicalDataTemplate DataType="{x:Type my:FileItem}">
            <Border Width="80"  Background="LightBlue" CornerRadius="2" Margin="1" >
                <StackPanel Orientation="Horizontal">
                    <Image Margin="2" />
                    <TextBlock Margin="2" Text="{Binding NodeName}" />
                </StackPanel>
            </Border>
        </HierarchicalDataTemplate>
    </TreeView.Resources>

Codebehind:

public class FileItem
{
    public string NodeName { get; set; }
    public string FullName { get; set; }
    public string Extension { get; set; }
}

public class ProgramItem : PropertyChangedBase
{
    private ObservableCollection<FileItem> fileItemCollection;
    ...

What I now want to do is hook a double click event on the node and open the relevant file.

    public void NodeDoubleClick(object sender, MouseButtonEventArgs e)
    {
        TreeViewItem treeViewItem = VisualUpwardSearch(e.OriginalSource as DependencyObject);

        if (treeViewItem != null)
        {
            //Open file
        }
    }

    private static TreeViewItem VisualUpwardSearch(DependencyObject source)
    {
        while (source != null && !(source is TreeViewItem))
            source = VisualTreeHelper.GetParent(source);

        return source as TreeViewItem;
    }

I can retrieve the double clicked node (treeviewitem) without a problem. The problem is I want to retrieve an object of FileItem from the node I double clicked to access the filepath property. Is this possible at all?

Answer 1

It is possible by resolving the DataContext of the TreeViewItem:

FileItem fileItem = (treeViewItem.DataContext as FileItem);

A more elegant way would be to use MouseInput Bindings and a Command in your FileItem class.

In your Datatemplate for FileItem:

<StackPanel Orientation="Horizontal">
    <StackPanel.InputBindings>
        <MouseBinding MouseAction="LeftDoubleClick" 
                      Command="{Binding OpenFileCommand}" />
    </StackPanel.InputBindings>
    <Image Margin="2" />
    <TextBlock Margin="2" Text="{Binding NodeName}" />
</StackPanel>

In your FileItem:

public class FileItem
{
   public FileItem()
   {
       this.OpenFileCommand 
           = new SimpleCommand(()=> Process.StartNew(this.FullName));
   }

   public string NodeName { get; set; }
   public string FullName { get; set; }
   public string Extension { get; set; }
   public ICommand OpenFileCommand { get; set;}
}

P.S.: If you are not used to WPF's Commands, a basic implementation of a simple ICommand could be:

public class SimpleCommand : System.Windows.Input.ICommand
{
    public SimpleCommand(Action action)
    {
        this.Action = action;
    }

    public Action Action { get; set; }

    public bool CanExecute(object parameter)
    {
        return (this.Action != null);
    }

    public event EventHandler CanExecuteChanged;

    public void Execute(object parameter)
    {
        if (this.Action != null)
        {
            this.Action();
        }
    }
}

Commands are much more effective for such szenarios. You dont need to walk the visual Tree and you do not need code behind at all.