How do I bind selectedItem property of WPFToolkit-Datagrid to my viewmodel property ?

Question

Hi,

I have a WPFToolkit-datagrid and a View-model class with a property - "SelectedGridItems" How do I bind selectedItem property of WPFToolkit-Datagrid to my viewmodel property ("SelectedGridItems") ?

Answer 1

This is code for WPF4's DataGrid, I don't have access to Toolkit at the moment, but I doubt it is different.

For binding a single row in a datagrid:

<DataGrid ItemsSource="{Binding ViewModelCollectionProperty}"
SelectedItem="{Binding Path=ViewModelProperty}">

</DataGrid>

To bind multiple selected rows, your best bet is probably to create an attached property which maintains a collection of selected items which can then be data bound to viewmodel.

EDIT -- added link below

See here for article about creating an attached property doing very similar to what you want: http://alexshed.spaces.live.com/Blog/cns!71C72270309CE838!149.entry

Answer 2

Here is an attached property that hooks to the SelectionChanged event of the ListBox and populates a list of selected items to the ViewModel. You can simply change "ListBox" to "DataGrid".

http://marlongrech.wordpress.com/2009/06/02/sync-multi-select-listbox-with-viewmodel/

Edit: Adding source code for DataGrid version...

/// <summary>
/// Attached property that stores the selected items of a DataGrid
/// </summary>
public static class DataGridService
{
   #region SelectedItems

   /// <summary>
   /// SelectedItems Attached Dependency Property
   /// </summary>
   public static readonly DependencyProperty SelectedItemsProperty = DependencyProperty.RegisterAttached(
       "SelectedItems", 
       typeof(IList), 
       typeof(DataGridService),
       new FrameworkPropertyMetadata((IList)null, new PropertyChangedCallback(OnSelectedItemsChanged)));

   /// <summary>
   /// Gets the SelectedItems property.
   /// </summary>
   /// <param name="d"><see cref="DependencyObject"/> to get the property from</param>
   /// <returns>The value of the SelectedItems property</returns>
   public static IList GetSelectedItems(DependencyObject d)
   {
      return (IList)d.GetValue(SelectedItemsProperty);
   }

   /// <summary>
   /// Sets the SelectedItems property.
   /// </summary>
   /// <param name="d"><see cref="DependencyObject"/> to set the property on</param>
   /// <param name="value">value of the property</param>
   public static void SetSelectedItems(DependencyObject d, IList value)
   {
      d.SetValue(SelectedItemsProperty, value);
   }

   /// <summary>
   /// Handles changes to the SelectedItems property.
   /// </summary>
   /// <param name="d"><see cref="DependencyObject"/> that fired the event</param>
   /// <param name="e">A <see cref="DependencyPropertyChangedEventArgs"/> that contains the event data.</param>
   private static void OnSelectedItemsChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
   {
      var grid = (DataGrid)d;
      ReSetSelectedItems(grid);
      grid.SelectionChanged += delegate
      {
         ReSetSelectedItems(grid);
      };
   }

   /// <summary>
   /// Sets the selected items collection for the specified <see cref="DataGrid"/>
   /// </summary>
   /// <param name="grid"><see cref="DataGrid"/> to use for setting the selected items</param>
   private static void ReSetSelectedItems(DataGrid grid)
   {
      IList selectedItems = GetSelectedItems(grid);
      selectedItems.Clear();
      if (grid.SelectedItems != null)
      {
         foreach (var item in grid.SelectedItems)
         {
            selectedItems.Add(item);
         }
      }
   }

   #endregion
}

In the XAML:

<tk:DataGrid ... local:DataGridService.SelectedItems="{Binding Path=MyCollection}" SelectionMode="Extended">

"MyCollection" should be an ObservableCollection in your ViewModel.