Use different template for last item in a WPF itemscontrol - wpf

Question

I'm using a custom template in my itemscontrol to display the following result:
item 1, item 2, item3,
I want to change the template of the last item so the result becomes:
item 1, item2, item3
The ItemsControl:
<ItemsControl ItemsSource="{Binding Path=MyCollection}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal" IsItemsHost="True"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding Path=Name}"/>
<TextBlock Text=", "/>
</StackPanel>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Is there anyone who can give a solution for my problem? Thank you!

Answer 1

I've found the solution for my problem using only XAML. If there is anybody who needs to do the same, use this:
<ItemsControl ItemsSource="{Binding Path=MyCollection}">
<ItemsControl.ItemsPanel>
<ItemsPanelTemplate>
<StackPanel Orientation="Horizontal" IsItemsHost="True"/>
</ItemsPanelTemplate>
</ItemsControl.ItemsPanel>
<ItemsControl.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<TextBlock x:Name="comma" Text=", "/>
<TextBlock Text="{Binding}"/>
</StackPanel>
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource PreviousData}}" Value="{x:Null}">
<Setter TargetName="comma" Property="Visibility" Value="Collapsed"/>
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>

Answer 2

You can use DataTemplateSelector, in SelectTemplate() method you can check whether item is the last and then return an other template.
In XAML:
<ItemsControl.ItemTemplate>
<DataTemplate>
<ContentPresenter
ContentTemplateSelector = "{StaticResource MyTemplateSelector}">
In Code behind:
private sealed class MyTemplateSelector: DataTemplateSelector
{
public override DataTemplate SelectTemplate(
object item,
DependencyObject container)
{
// ...
}
}

Answer 3

This solution affects the last row and updates with changes to the underlying collection:
CodeBehind
The converter requires 3 parameters to function properly - the current item, the itemscontrol, the itemscount, and returns true if current item is also last item:
class LastItemConverter : IMultiValueConverter
{
public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture)
{
int count = (int)values[2];
if (values != null && values.Length == 3 && count>0)
{
System.Windows.Controls.ItemsControl itemsControl = values[0] as System.Windows.Controls.ItemsControl;
var itemContext = (values[1] as System.Windows.Controls.ContentPresenter).DataContext;
var lastItem = itemsControl.Items[count-1];
return Equals(lastItem, itemContext);
}
return DependencyProperty.UnsetValue;
}
public object[] ConvertBack(object value, Type[] targetTypes, object parameter, CultureInfo culture)
{
throw new NotImplementedException();
}
}
XAML
The Data-Trigger for a DataTemplate, that includes a textbox named 'PART_TextBox':
<DataTemplate.Triggers>
<DataTrigger Value="True" >
<DataTrigger.Binding>
<MultiBinding Converter="{StaticResource LastItemConverter}">
<Binding RelativeSource="{RelativeSource FindAncestor, AncestorType={x:Type ItemsControl}}" />
<Binding RelativeSource="{RelativeSource Self}"/>
<Binding RelativeSource="{RelativeSource FindAncestor, AncestorType={x:Type ItemsControl}}" Path="Items.Count"/>
</MultiBinding>
</DataTrigger.Binding>
<Setter Property="Foreground" TargetName="PART_TextBox" Value="Red" />
</DataTrigger>
</DataTemplate.Triggers>
The converter as a static resource in the Xaml
<Window.Resources>
<local:LastItemConverter x:Key="LastItemConverter" />
</Window.Resources>
SnapShot
And a snapshot of it in action
The code has been added to the itemscontrol from this 'codeproject'
https://www.codeproject.com/Articles/242628/A-Simple-Cross-Button-for-WPF
Note the last item's text in red

Answer 4

One question... I see you're using an ItemsControl as opposed to say a ListBox and that it appears to be bound to a collection of strings, and that you're only trying to display the resulting text without formatting the individual parts, which makes me wonder if your desired output is actually the string itself as mentioned in the question, and not an actual ItemsControl per se.
If I'm correct about that, have you considered just using a simple TextBlock bound to the items collection, but fed through a converter? Then Inside the converter, you would cast value to an array of strings, then in the Convert method, simply Join them using a comma as the separator which will automatically, only add them between elements, like so...
var strings = (IEnumerable<String>)value;
return String.Join(", ", strings);