Bubbling events in WPF? Simple Question

Question

This is probably a really easy fix, but I am inexperienced in working with events so I am just going to ask it.

I have a ListBox with ListBoxItems in it. These ListBoxItems will be binded to a data source so they will change. I need a MouseDown event to be raised when a MouseDown action is performed on any of these ListBoxItem (because I am doing drag and drop). Since the values are changing, I cannot expect to wire the events together in the XAML like the following

<ListBox Name="ListBox1">
    <ListBoxItem MouseDown="MouseDownEventName">Item A</ListBoxItem>
    <ListBoxItem MouseDown="MouseDownEventName">Item B</ListBoxItem>
    <ListBoxItem MouseDown="MouseDownEventName">Item C</ListBoxItem>
</ListBox>

This would be easy if I had static values, but since the values in the ListBox will change, I would prefer to write the following XAML

 <ListBox Name="ListBox1" MouseDown="MouseDownEventName">
     //Binded Values
</ListBox>

Then, when the ListBoxItem is selected, it would Bubble the event up to this MouseDownEventName, and I can grab ListBox1.SelectedItem at that time, the problem is, I am trying this right now, but it is not working. I have the following Code to handle the MouseDown, which is only rewriting label content at the moment to signify that the item has been MouseDown'ed.

    public partial class UserControl1 : UserControl
    {
    public UserControl1()
    {
        InitializeComponent();
    }

    private void ListBox_MouseDown(object sender, RoutedEventArgs e)
    {
        ListBox box = (ListBox)sender;
        if (box != null && box.SelectedItem != null)
        {

            DragDrop.DoDragDrop(box, ItemListBox.SelectedItem, DragDropEffects.Move);
            label1.Content = "MouseDown Event Fired";
        }
    } 
}

score 3 · Accepted Answer · edited May 23 '17 at 12:18

3

Using XAML, you can provide a template for different types contained within the form. For example, in this case, you can specify that ListBoxItem's fire off a certain event handler. This is the bulk of the XAML markup code (details found here: How to catch Click on ListboxItem when the item is templated?)

<ListBox>
    <ListBox.ItemContainerStyle>
        <Style TargetType="ListBoxItem">
            <EventSetter Event="PreviewMouseLeftButtonDown" Handler="ListBoxItem_PreviewMouseLeftButtonDown"/>
        </Style>
    </ListBox.ItemContainerStyle>
...
</ListBox>

Another thing to check before is to try and change your DragDrop.DoDragDrop() method call to something else to see if the issue has to do with that method. Since the Label's content is changing, I would imagine it has something to do with that method.

edited May 23 '17 at 12:18

Community

1
1

answered Jan 18 '11 at 18:46

pseudoramble

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So to make sure I am understanding this correctly, this would allow me to specify the source from which my List would be built, and then specify the structure of it, and declare the Event from which each can be triggered for? It worked BTW, but I am just wanting to make sure I understand it for the right reasons – TheJediCowboy Jan 18 '11 at 18:57
Glad to hear it! Yeah basically that's the idea. Imagine this code kind of like CSS is to HTML - You specify the kind of tag you want to modify and apply different attributes and properties to that tag. In this case, we added an EventSetter for each ListBoxItem. This saves you the trouble of specifying the a Clicked event handler for each ListBoxItem. – pseudoramble Jan 18 '11 at 19:29

Bubbling events in WPF? Simple Question

1 Answers1