Redigera

Dela via

How to: Navigate Through the Objects in a Data CollectionView

  • Artikel

Views allow the same data collection to be viewed in different ways, depending on sorting, filtering, or grouping. Views also provide a current record pointer concept and enable moving the pointer. This example shows how to get the current object as well as navigate through the objects in a data collection using the functionality provided in the CollectionView class.

Example

In this example, myCollectionView is a CollectionView object that is a view over a bound collection.

In the following example, OnButton is an event handler for the Previous and Next buttons in an application, which are buttons that allow the user to navigate the data collection. Note that the IsCurrentBeforeFirst and IsCurrentAfterLast properties report whether the current record pointer has come to the beginning and the end of the list respectively so that MoveCurrentToFirst and MoveCurrentToLast can be called as appropriately.

The CurrentItem property of the view is cast as an Order to return the current order item in the collection.

//OnButton is called whenever the Next or Previous buttons
//are clicked to change the currency
  private void OnButton(Object sender, RoutedEventArgs args)
  {
      Button b = sender as Button;

      switch (b.Name)
      {
          case "Previous":
              myCollectionView.MoveCurrentToPrevious();

              if (myCollectionView.IsCurrentBeforeFirst)
              {
                  myCollectionView.MoveCurrentToLast();
              }
              break;

          case "Next":
              myCollectionView.MoveCurrentToNext();
              if (myCollectionView.IsCurrentAfterLast)
              {
                  myCollectionView.MoveCurrentToFirst();
              }
              break;

          o = myCollectionView.CurrentItem as Order;
          // TODO: do something with the current Order o
      }
  }

'OnButton is called whenever the Next or Previous buttons
'are clicked to change the currency
  Private Sub OnButton(ByVal sender As Object, ByVal args As RoutedEventArgs)
      Dim b As Button = TryCast(sender, Button)

      Select Case b.Name
          Case "Previous"
              myCollectionView.MoveCurrentToPrevious()

              If myCollectionView.IsCurrentBeforeFirst Then
                  myCollectionView.MoveCurrentToLast()
              End If

          Case "Next"
              myCollectionView.MoveCurrentToNext()
              If myCollectionView.IsCurrentAfterLast Then
                  myCollectionView.MoveCurrentToFirst()
              End If
              Exit Select

          o = TryCast(myCollectionView.CurrentItem, Order)
          ' TODO: do something with the current Order o 
      End Select
  End Sub

See also