Question

I am trying to bind a context menu item to a command that I have defined in my ViewModel. The context menu sits inside a ListView that I also have bound to a CollectionViewSource, and this I think is the cause of the problem.

I have managed to bind the selected item in the listView collection to my ViewModel, but when I am trying to use the same way to bind the context menu item command to my ViewModel it doesn’t work. I hope that anybody have the time to read through all the code below and give me some idea about what I am doing wrong.

Ps. I have had to change some of the names in order to not give away what the application is about.

In my ViewModel I have defined the followning:

public ObservableCollection<ListItemViewModel> ListViewItemViewModels {get; set;}

public MyListItem SelectedListItemViewModel {get; set;}

private RelayCommand _runCommand;
public ICommand RunCommand {
  get {
     return _runCommand ??
       ( _runCommand = new RelayCommand( param => RunReport(), param => CanRunReport ) );
  }
}

private void RunReport() {
    Logger.Debug("Run report");
}

Then in my View I have set upp a ListView as follows:

<ListView DataContext="{StaticResource ListGroups}"
   ItemsSource="{Binding}" 
   ItemContainerStyle="{StaticResource ListItemStyle}" 
   IsSynchronizedWithCurrentItem="True" 
   SelectedItem="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Grid},AncestorLevel=1 }, Path=DataContext.SelectedListItem, UpdateSourceTrigger=PropertyChanged}" 
   Margin="10,10,0,10">
   <ListView.GroupStyle>
        <StaticResourceExtension ResourceKey="AccountGroupStyle"/>
   </ListView.GroupStyle>
   <ListView.View>
       <GridView>
            <GridViewColumn Header="Title" DisplayMemberBinding="{Binding Path=DisplayTitle}"/>
            <GridViewColumn Header="Date" DisplayMemberBinding="{Binding Path=DateString}"/>
        </GridView>
   </ListView.View>
   <ListView.ContextMenu>
       <ContextMenu Name="ListViewContextMenu">
          <MenuItem Header="Run" Command="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Grid},AncestorLevel=1 }, Path=DataContext.RunCommand}"/>
       </ContextMenu>
   </ListView.ContextMenu>


</ListView>

The CollectionViewSource is defined as follows:

<DataTemplate x:Key="ListViewListTemplate" DataType="{x:Type ViewModels:ListItemViewModel}">
    <StackPanel Orientation="Vertical">
        <TextBlock Text="{Binding Path=DisplayTitle}" Margin="8,0,0,0"/>
    </StackPanel>
</DataTemplate>

<CollectionViewSource Source="{Binding Path=ListItemViewModels}" x:Key="ListItemGroups">
    <CollectionViewSource.GroupDescriptions>
        <PropertyGroupDescription PropertyName="ListItemGroupName"/>
    </CollectionViewSource.GroupDescriptions>
    <CollectionViewSource.SortDescriptions>
        <ComponentModel:SortDescription PropertyName="Index" Direction="Ascending"/>
        <ComponentModel:SortDescription PropertyName="DisplayTitle" Direction="Ascending"/>
    </CollectionViewSource.SortDescriptions>
</CollectionViewSource>

<GroupStyle x:Key="ListItemGroupStyle">
    <GroupStyle.HeaderTemplate>
        <DataTemplate>
            <!-- The text binding here is refered to the property name set above in the propertyGroupDescrition -->
            <TextBlock x:Name="text" Background="{StaticResource DateGroup_Background}" FontWeight="Bold" Text="{Binding Path=Name}"
                      Foreground="White"
                     Margin="1"
                     Padding="4,2,0,2"/>

        </DataTemplate>
    </GroupStyle.HeaderTemplate>
</GroupStyle>

<Style x:Key="ListItemStyle" TargetType="{x:Type ListViewItem}">

    <Setter Property="HorizontalContentAlignment" Value="Stretch"/>

    <!-- 
  Bind the IsSelected property of a ListViewItem to the 
  IsSelected property of a ReconciliationTaskViewModel object.
  -->
    <Setter Property="IsSelected" Value="{Binding Path=IsSelected, Mode=TwoWay}" />
    <Style.Triggers>
        <MultiTrigger>
            <MultiTrigger.Conditions>
                <Condition Property="ItemsControl.AlternationIndex" Value="1" />
                <Condition Property="IsSelected" Value="False" />
                <Condition Property="IsMouseOver" Value="False" />
            </MultiTrigger.Conditions>
            <Setter Property="Background" Value="#EEEEEEEE" />
        </MultiTrigger>
    </Style.Triggers>
</Style>

Answer 1

The cause of the problem is that the ContextMenu isn’t part of either the logical or visual tree of the ListView, so RelativeSource/FindAncestor doesn’t work, and the DataContext is not inherited.

I posted a solution to this problem a few months ago, you can use it as follows:

<ListView ...>
    <ListView.Resources>
        <local:BindingProxy x:Key="proxy" Data="{Binding}" />
    </ListView.Resources>

    ...

   <ListView.ContextMenu>
       <ContextMenu Name="ListViewContextMenu">
          <MenuItem Header="Run" Command="{Binding Source={StaticResource proxy}, Path=Data.RunCommand}"/>
       </ContextMenu>
   </ListView.ContextMenu>


    ...

</ListView>