Question

I am making my first gui in C# and I have watched/read a ton of tutorials about WPF and MVVM(that’s the approach I’m using), but I am stuck on something that intuitively should be rather simple to accomplish. I have a listbox, and above it I would like to display a textblock or label that would say “Please select item from list” and then disappear once an item is selected.

How can I accomplish this? Would it require writing in the code-behind? Most tutorials I have read discourage ever using the code-behind so I would prefer a different solution. I assume this is not possible to do directly from within XAML, so would I need to create a ViewModel variable to hold the listbox state?? If so, then how could I make a textblock/label dependent on a variable?

Answer 1

For doing this in XAML only

<StackPanel>
    <TextBlock Text="Please select an item!">
        <TextBlock.Style>
            <Style TargetType="TextBlock">
                <Setter Property="Visibility" Value="Collapsed" />
                <Style.Triggers>
                    <DataTrigger Binding="{Binding SelectedItem, ElementName=lb}" Value="{x:Null}">
                        <Setter Property="Visibility" Value="Visible" />
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </TextBlock.Style>
    </TextBlock>
    <ListBox Name="lb" ItemsSource="12345" />
</StackPanel>

ItemsSource="12345" will create five rows for demonstration only.