Wpf主要详细列表视图绑定

Question

I have a this model (it's not the actual code, I omitted the INotifyPropertyChanged implementation for clarity).

  public class Project
  {
       public ObservableCollection<Component> Components { get; set; }
  }

  public class Component
  {
       public ObservableCollection<Item> Items { get; set; }
  }

  public class Item 
  {
       public LookupItem LookupItem { get; set; }
  }

And this is the ViewModel

  public class ViewModel
  {
        public Project Project { get; set; }
        public Components { get { return Project.Components; } }

        public ObservableCollection<LookupItem> LookupItems { get; set; }
  }

In the view I have two listviews one showing the Components and the other binded to the first one showing the Items of the selecte Component. The latter listview should have a combobox for any Item in order to change the lookupitem, but I cannot bind it.

This is the xaml

   <ListView x:Name="list" ItemsSource="{Binding Components}">
       ......
   </LIstView>

and the latter

  <ListView  ItemsSource="{Binding Items}" DataContext="{Binding SelectedItem, ElementName=list}">
....
<GridViewColumn Width="140">
    <GridViewColumnHeader Tag="Publisher" Content="Item" />
    <GridViewColumn.CellTemplate>
        <DataTemplate>
            <Grid HorizontalAlignment="Stretch">
                <ComboBox SelectedItem="{Binding Path=Item}" ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type local:ViewModel}}, Path=LookupItems, Mode=TwoWay }" DisplayMemberPath="Name" />
            </Grid>
        </DataTemplate>
    </GridViewColumn.CellTemplate>
</GridViewColumn>

I cannot make the combobox populate. Wpf gives me the error

  System.Windows.Data Error: 4 : Cannot find source for binding with 
  reference 'RelativeSource FindAncestor, AncestorType='Projectname.ViewModels.ViewModel', AncestorLevel='1''. BindingExpression:Path=LookupItems; DataItem=null; target element is 'ComboBox' (Name=''); target property is 'ItemsSource' (type 'IEnumerable')

Answer 1

Try adding your ViewModel as DataContext, eg. for Window , like this:

<Window.DataContext>
    <local:ViewModel />
</Window.DataContext>

or in code-behind:

var viewModel = new ViewModel();
this.DataContext = viewModel;

And in DataTemplate write this:

<DataTemplate>
    <Grid HorizontalAlignment="Stretch">
        <ComboBox ItemsSource="{Binding Path=DataContext.LookupItems, 
                                        RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}},
                                        Mode=TwoWay}" ... />
    </Grid>
</DataTemplate>