wpf binding to element

What does the selection have to do with the Touches? (Also the ElementName is off)

I would try this:

IsEnabled="{Binding SelectedItems.Count, ElementName=BannedItemsListBox}"

Explanation: Basically the binding system tries to convert the input to the property at hand, a boolean, so when it gets an integer, 0 will be converter to false, anything higher to true. So the Button will be enabled if one or more items are selected.

<Button Content="Button"
        Height="23"
        HorizontalAlignment="Left"
        Margin="138,12,0,0"
        Name="button1"
        VerticalAlignment="Top"
        Width="75"
        Click="button1_Click">
    <Button.Style>
        <Style>
            <Setter Property="Button.IsEnabled"
                    Value="True" />
            <Style.Triggers>
                <DataTrigger Binding="{Binding ElementName=lstTest , Path=SelectedItem}"
                             Value="{x:Null}">
                    <Setter Property="Button.IsEnabled"
                            Value="False" />
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </Button.Style>
</Button>