Question

So I have a Listbox:

<ListBox Grid.Row="0" Grid.Column="1" Grid.RowSpan="2"> //<----Item's Data Source Method Call Here?
    <ListBox.ItemsPanel>
        <ItemsPanelTemplate>
            <VirtualizingStackPanel
             Orientation="Horizontal"
             IsItemsHost="true"  />
        </ItemsPanelTemplate>
     </ListBox.ItemsPanel>
     <ListBox.ItemTemplate>
       <DataTemplate>
          <StackPanel Grid.Row="0" Grid.Column="1" Grid.RowSpan="2" Orientation="Vertical">
             <Label Content="{Binding Address1}"></Label>
             <Label Content="{Binding Address2}"></Label>
             <Label Content="{Binding Town}"></Label>
             <Label Content="{Binding Postcode}"></Label>
             <Label Content="{Binding Country}"></Label>
             <CheckBox Content="{Binding Include}"></CheckBox>
          </StackPanel>
       </DataTemplate>
     </ListBox.ItemTemplate>
</ListBox>

What I would like to do is set the item’s data source to a list of addresses all of which have the same postal code. So I need a list of the current addresses in an Observable Collection with the same postcode. To generate such a list of addresses would only take a call to a method which accepts the current postcode as a an argument but I don’t know how to call a method that requires an argument from a static datasource.

Can anyone help?

Answer 1

Create a view with a Collection property and a PostCode property. Bind the PostCode TwoWay, let the setter raise OnPropertyChanged for the Collection property, and let the collection property return a collection based on the current value of the PostCode property.

internal class MyView : INotifyPropertyChanged {
   private string _postCode;

   public string PostCode {
      get { return _postCode; }
      set {
         _postCode = value;
         OnPropertyChanged("PostCode");
         OnPropertyChanged("FilteredItems");
      }
   }

   public ObservableCollection<Address> Items { get; set; }

   public IEnumerable<Address> FilteredItems {
      get { return Items.Where(o => o.PostCode == _postCode).ToArray(); }
   }

   public event PropertyChangedEventHandler PropertyChanged;

   private void OnPropertyChanged( string propertyName ) {
      if( PropertyChanged != null ) {
         PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
      }
   }
}

<Grid DataContext="{Binding Path=myViewInstance}">
   <TextBox Text="{Binding Path=PostCode, Mode=TwoWay}"/>
   <ListBox Grid.Row="0" Grid.Column="1" Grid.RowSpan="2" ItemsSource="{Binding Path=FilteredItems}">
      <ListBox.ItemsPanel>
         <ItemsPanelTemplate>
            <VirtualizingStackPanel
               Orientation="Horizontal"
               IsItemsHost="true"  />
         </ItemsPanelTemplate>
      </ListBox.ItemsPanel>
      <ListBox.ItemTemplate>
         <DataTemplate>
            <StackPanel Grid.Row="0" Grid.Column="1" Grid.RowSpan="2" Orientation="Vertical">
               <Label Content="{Binding Address1}"></Label>
               <Label Content="{Binding Address2}"></Label>
               <Label Content="{Binding Town}"></Label>
               <Label Content="{Binding PostCode}"></Label>
               <Label Content="{Binding Country}"></Label>
               <CheckBox Content="{Binding Include}"></CheckBox>
            </StackPanel>
         </DataTemplate>
      </ListBox.ItemTemplate>
   </ListBox>
</Grid>

Note: My “Address” class might differ from yours.