How to pass listbox selecteditem as command parameter in a button?

Question

Here is my situation:

<ListBox ItemsSource="{Binding Path=AvailableUsers}">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding Path=Id}"/>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>
<Button Command="{Binding Path=Load}" CommandParameter={???? What goes here ????}/>

What I want is to pass the Id that is currently selected in the ListBox. I have a viewmodel behind the scenes that essentially looks like this:

public class ViewModel : DependencyObject
{
    ICommand Load { get; set; }

    // dependency property but I didn't bother to write it out like one
    List<User> AvailableUsers { get; set}
}

How can I send the currently selected item using the xaml?

Solution

Try this:

1. Name your listbox
2. Update the CommandParameter to:

   CommandParameter="{Binding ElementName=listBox1,Path=SelectedItem}"