Why e.Source depends on TreeView populating method?

问题

I have two trees:

1. fooTree - made up of elements,
2. barTree - constructed by

Both trees have MouseRightButtonDown event, but the e.Source type differs:

1. fooTree - System.Windows.Controls.TreeViewItem
2. barTree - System.Windows.Controls.TreeView

Why e.Source differs? Also, how can I get the clicked item for the barTree?

Markup:

    <TreeView Name="fooTree" MouseRightButtonDown="fooTree_MouseDown">
        <TreeViewItem Header="foo"></TreeViewItem>
        <TreeViewItem Header="foo"></TreeViewItem>
    </TreeView>

    <TreeView Name="barTree" MouseRightButtonDown="barTree_MouseDown" ItemsSource="{Binding BarItems}">
        <TreeView.ItemTemplate>
            <HierarchicalDataTemplate>
                <TextBlock Text="{Binding}" />
            </HierarchicalDataTemplate>
        </TreeView.ItemTemplate>
    </TreeView>

Code:

public partial class Window1 : Window
{
    public Window1()
    {
        InitializeComponent();
        this.DataContext = this;
    }

    public string[] BarItems
    {
        get { return new string[] { "bar", "bar" }; }
    }

    private void barTree_MouseDown(object sender, MouseButtonEventArgs e) 
    {
    }

    private void fooTree_MouseDown(object sender, MouseButtonEventArgs e) 
    {
    }
}

回答1:

Don't know why this happens, but at least I have found a solution:

http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/f0d3af69-6ecc-4ddb-9526-588b72d5196b/

1. If your handler is on the TreeView, use the OriginalSource property in the event arguments and walk up the visual parent chain until you find a TreeViewItem. Then, select it. You can walk the visual parent chain by using System.Windows.Media.VisualTreeHelper.GetParent.

2. You could try registering a class handler for type TreeViewItem and the mouse down event. Then, your handler should only be called when mouse events pass through TreeViewItem elements.

3. You could register a class handler for type TreeViewItem and the context menu opening event.

So my code is:

private void OnMouseRightButtonDown(object sender, MouseButtonEventArgs e)
{
    TreeViewItem treeViewItem = VisualUpwardSearch<TreeViewItem>(e.OriginalSource as DependencyObject) as TreeViewItem;
}

static DependencyObject VisualUpwardSearch<T>(DependencyObject source)
{
    while (source != null && source.GetType() != typeof(T))
        source = VisualTreeHelper.GetParent(source);

    return source;
}

回答2:

You can get the clicked item in the bartree using:

((e.Source) as TreeView).SelectedValue

But be aware that the item must actually selected first (using leftMouse). The item is not immediately selected using rightMouse...

来源：https://stackoverflow.com/questions/593194/why-e-source-depends-on-treeview-populating-method