silverlight template for ListBox and DataGrid when empty?

So are there any available in 开发者_StackOverflow社区the SL4?

I need to display some sort of info when no data is presented in the ListBox and/Or DataGrid when they are empty.

If anyone is familiar with any of these and can provide examples or links, I would appreciate it.

Thanks,

Voodoo

I have not tried this my self yet, but you might be interested in the blog post link below, which provides a solution for the DataGrid, which you could probably adapt for ListBoxes as well.

http://subodhnpushpak.wordpress.com/2009/05/18/empty-data-template-in-silverlight-datagrid/

I've come up with a simpler solution for listboxes that works for me in 99% of the cases. Once setup as a resource, all you have to do is change the Tag property on the listbox to get all the functionality to work.

First, I modify the default template of the Listbox to include a new grid and a textbox like so:

Original XAML

<Border Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="3" Margin="0">
    <ScrollViewer x:Name="ScrollViewer" Background="Transparent" BorderBrush="Transparent" BorderThickness="0" Margin="0" Padding="0" TabNavigation="{TemplateBinding TabNavigation}">
        <ItemsPresenter Margin="0,0" />
    </ScrollViewer>
</Border>

New XAML

<Border Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="3" Margin="0">
    <Grid >
        <TextBlock Text="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=Tag}" VerticalAlignment="Center" HorizontalAlignment="Center" Visibility="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=ItemsSource.Count, Converter={StaticResource ListCount2Visibility}}" Foreground="{StaticResource NormalFontBrush}" FontSize="{StaticResource DefaultFontSize}" />

        <ScrollViewer x:Name="ScrollViewer" Background="Transparent" BorderBrush="Transparent" BorderThickness="0" Margin="0" Padding="0" TabNavigation="{TemplateBinding TabNavigation}">
            <ItemsPresenter Margin="0,0" />
        </ScrollViewer>
    </Grid>
</Border>

The textblock visibility property is bound to a custom converter entitled ListCount2Visibility which looks like this:

public sealed class ListCount2Visibility : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value != null && (int)value > 0 )
            return "Collapsed";
        else
            return "Visible";

    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }
}

The value converter checks if the ItemSource.Count == 0...if it is, it sets the visibility to visible. Otherwise, it collapses it.

The Text property of the new textblock is then bound to the Tag property of the listbox. (This isn't ideal but it is the quickest way to get the text into the control. Obviously this won't work if you use the tag property for other things).

So basically, you set the tag to the message you want to display, and anytime there are no items in the list, the textbox is shown (centered horizontally and vertically). During development, your message will show since the list is empty (assuming now design time datacontext) which makes it nice to visualize the text.

That is really all there is to it.

If you want, you can even bind the tag property of the listbox to your viewmodel to change the text. So you could do things like "loading...." while items are returned from the database and then change it to the "empty list" message after everything loads. (of course busy indicator is probably better)