WPF: How to assign a Click handler for a Button defined in a style

Question

I have ListBox that is supposed to show a list of Fields. When empty, I wanted to have inside the ListBox a "Add Field" button. So, I created a Style for the empty case that adds the button. I needed to add a handler for the Click event for the button to create a new Field and add it to the list, so I used an EventSetter to attach the handler. Here is the code that I have.

<ListBox.Style>
  <Style TargetType="ListBox" BasedOn="{StaticResource {x:Type ListBox}}">
    <Style.Triggers>
      <Trigger Property="HasItems" Value="False">
        <Setter Property="Template">
          <Setter.Value>
            <ControlTemplate>
              <Button Content="Add field" Height="20">
                <Button.Style>
                  <Style TargetType="{x:Type Button}">
                    <EventSetter Event="Click" Handler="AddField_Click" />
                  </Style>
                </Button.Style>
              </Button>
            </ControlTemplate>
          </Setter.Value>
        </Setter>
      </Trigger>
    </Style.Triggers>
  </Style>
</ListBox.Style>

The problem is that when I compile, I get the following error on the line where the EventSetter tag is:

error MC4007: The event 'Click' cannot be specified on a Target tag in a Style. 
Use an EventSetter instead.

I am stumped. I already use an EventSetter. How do I resolve this? Is there some other way of specifying the EventSetter that I should use?

Answer 1

Try creating a Style and assign that to Button. Like,

<ListBox>
    <ListBox.Resources>
        <Style x:Key="ButtonStyle" TargetType="{x:Type Button}">
            <EventSetter Event="Button.Click" Handler="AddField_Click" />
        </Style>
    </ListBox.Resources>
    <ListBox.Style>
        <Style TargetType="ListBox" BasedOn="{StaticResource {x:Type ListBox}}">
            <Style.Triggers>
                <Trigger Property="HasItems" Value="False">
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate>
                                <Button Content="Add field" Height="20" 
                                        Style="{StaticResource ButtonStyle}">
                                </Button>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Trigger>
            </Style.Triggers>
        </Style>
    </ListBox.Style>
</ListBox>

This should work.