WPF items not visible when grouping is applied - wpf

Question

I'm having this strange issue with my ItemsControl grouping. I have the following setup:
<ItemsControl Margin="3" ItemsSource="{Binding Communications.View}" >
<ItemsControl.GroupStyle>
<GroupStyle>
<GroupStyle.ContainerStyle>
<Style TargetType="{x:Type GroupItem}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type GroupItem}">
<Expander>
<Expander.Header>
<Grid>
<Grid.ColumnDefinitions >
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<TextBlock Text="{Binding ItemCount, StringFormat='{}[{0}] '}" FontWeight="Bold" />
<TextBlock Grid.Column="1" Text="{Binding Name, Converter={StaticResource GroupingFormatter}, StringFormat='{}Subject: {0}'}" FontWeight="Bold" />
</Grid>
</Expander.Header>
<ItemsPresenter />
</Expander>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</GroupStyle.ContainerStyle>
</GroupStyle>
</ItemsControl.GroupStyle>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<TextBlock FontWeight="Bold" Text="{Binding Inspector, Converter={StaticResource NameFormatter}, StringFormat='{}From {0}:'}" Margin="3" />
<TextBlock Text="{Binding SentDate, StringFormat='{}{0:dd/MM/yy}'}" Grid.Row="1" Margin="3"/>
<TextBlock Text="{Binding Message }" Grid.Column="1" Grid.RowSpan="2" Margin="3"/>
<Button Command="vm:CommunicationViewModel.DeleteMessageCommand" CommandParameter="{Binding}" HorizontalAlignment="Right" Grid.Column="2">Delete</Button>
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
In my ViewModel, I expose a CollectionViewSource named 'Communications'. I proceed to adding a grouping patter like so:
Communications.GroupDescriptions.Add(new PropertyGroupDescription("Subject"));
Now, the problem i'm experience is the grouping work fine, but I can't see any items inside the groups. What am I doing wrong? Any pointers would be much appreciated.

Answer 1

I can't seem to reproduce the problem - I assume you are using a CollectionViewSource? It might be because you bound to the View property directly.
Here's the C# code I used:
public class Communication
{
public string Subject { get; set; }
public string Body { get; set; }
}
public partial class Window1 : Window
{
public Window1()
{
InitializeComponent();
var source = (CollectionViewSource)Resources["Communications"];
source.Source = new List<Communication>()
{
new Communication { Subject = "WPF 4.0", Body = "I love what's happening with 4.0"},
new Communication { Subject = "WPF 4.0", Body = "I hear the text rendering is the best feature"},
new Communication { Subject = "Blend 3.0", Body = "Behaviors in Blend 3 change everything"}
};
source.GroupDescriptions.Add(new PropertyGroupDescription("Subject"));
}
}
Here is the XAML - it's the same as yours but with a couple of things removed since I don't have your converters or commands:
<Window
x:Class="GroupStyleDemo.Window1"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="Window1" Height="300" Width="300"
>
<Window.Resources>
<CollectionViewSource x:Key="Communications" />
</Window.Resources>
<Grid>
<ItemsControl Margin="3" ItemsSource="{Binding Source={StaticResource Communications}}" >
<ItemsControl.GroupStyle>
<GroupStyle>
<GroupStyle.ContainerStyle>
<Style TargetType="{x:Type GroupItem}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type GroupItem}">
<Expander>
<Expander.Header>
<Grid>
<Grid.ColumnDefinitions >
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<TextBlock Text="{Binding ItemCount, StringFormat='{}[{0}] '}" FontWeight="Bold" />
<TextBlock Grid.Column="1" Text="{Binding Path=Name}" FontWeight="Bold" />
</Grid>
</Expander.Header>
<ItemsPresenter />
</Expander>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</GroupStyle.ContainerStyle>
</GroupStyle>
</ItemsControl.GroupStyle>
<ItemsControl.ItemTemplate>
<DataTemplate>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition />
<RowDefinition />
</Grid.RowDefinitions>
<TextBlock Text="{Binding Body }" Grid.Column="1" Grid.RowSpan="2" Margin="3"/>
</Grid>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
</Window>

Answer 2

After hitting this problem myself I discovered the cause: the template for ItemsControl directly including a panel with IsItemsHost="true".
You must insert an ItemPresenter into your template and set the ItemsControl.ItemsPanel property instead.