WPF Grouping In Listbox

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WPF

MVVM

grouping

Hi Guys,

So I am attempting to group data in the Listbox in my MVVM WPF application.
I have read both the following links which is where I have sourced how to start this from:

mvvm-grouping-items-in-listview[^]
karl shifflett - wpf-sample-series-listbox-grouping-sorting-subtotals-and-collapsible-regions/[^]

Now I am getting an issue, that for the life of me I cannot explain as I seem to be doing things pretty much the same (bar a few changes).

The issue
This line:

<ItemsPresenter Visibility="{Binding IsChecked, Converter={StaticResource booleanToVisibilityConverter}, ElementName=btnShowHide}" Grid.Row="1" Margin="11,0,0,3.5" />

Is being marked with an error:
Value cannot be null. Parameter name: element

Now, this does not stop the program compiling but it crashes at run time when I try to load the view.

I appologise now for the following largeish code dump, but below is the XAML for the listbox control I am using.

<ListBox Grid.Row="2" Margin="5" DataContext="{DynamicResource SurveyDatesGroup}"
        ItemsSource="{Binding IsAsync=True}">
      <ListBox.GroupStyle>
         <GroupStyle>
            <GroupStyle.ContainerStyle>
               <Style TargetType="{x:Type GroupItem}">
                  <Setter Property="Template">
                      <Setter.Value>
                           <ControlTemplate TargetType="{x:Type GroupItem}">
                                <Grid>
                                   <Grid.RowDefinitions>
                                        <RowDefinition />
                                        <RowDefinition />
                                   </Grid.RowDefinitions>
                                <Grid removed="Black" x:Name="gridTemplate" Height="26"
				      VerticalAlignment="Center">
                                    <Grid.Resources>
                                       <Style TargetType="{x:Type TextBlock}">
                                          <Setter Property="FontSize" Value="14" />
                                          <Setter Property="Foreground" Value="White" />
                                          <Setter Property="VerticalAlignment" Value="Center" />
                                       </Style>
                                    </Grid.Resources>
                                    <Grid.ColumnDefinitions>
                                         <ColumnDefinition Width="Auto" />
                                         <ColumnDefinition Width="*" />
                                         <ColumnDefinition Width="45" />
                                         <ColumnDefinition Width="30" />
                                         <ColumnDefinition Width="110" />
                                    </Grid.ColumnDefinitions>
                                    <ToggleButton x:Name="btnShowHide" IsChecked="True" 
                                          Margin="3.5" />
                                    <TextBlock Grid.Column="1" Text="{Binding Name}" 
                                          Margin="3.5,0" />
                                    <TextBlock Grid.Column="2" Text="Count:" />
                                    <TextBlock Grid.Column="3" Text="{Binding ItemCount}"
					TextAlignment="Right" Margin="0,0,11,0" />
                                </Grid>
                                <ItemsPresenter Visibility="{Binding IsChecked, Converter={StaticResource booleanToVisibilityConverter}, ElementName=btnShowHide}" Grid.Row="1" Margin="11,0,0,3.5" />
                             </Grid>
                             <ControlTemplate.Triggers>
                                  <DataTrigger Binding="{Binding IsBottomLevel}" Value="True">
                                         <Setter TargetName="gridTemplate" Property="Background" Value="#FF965F00" />
                                   </DataTrigger>
                             </ControlTemplate.Triggers>
                         </ControlTemplate>
                         </Setter.Value>
                     </Setter>
                  </Style>
              </GroupStyle.ContainerStyle>
         </GroupStyle>
     </ListBox.GroupStyle>
     <ListBox.ItemTemplate>
         <DataTemplate>
             <Grid>
                <Grid.ColumnDefinitions>
                     <ColumnDefinition />
                     <ColumnDefinition />
                     <ColumnDefinition />
                 </Grid.ColumnDefinitions>
                 <TextBlock Text="{Binding MQY}"/>
                 <TextBlock Grid.Column="2" Text="{Binding DateRange}"/>
             </Grid>
        </DataTemplate>
    </ListBox.ItemTemplate>
</ListBox>

Any help with solving this would be greatly appreciated, if you need more info let me know.