Prerequisite Knowledge DataGrid Fundamentals: Object Model Overview DataGrid Fundamentals: DataGridCollectionView Class

The DataGridDetailDescription class provides information about a detail relation whose content will be displayed as the details of the data items in a grid or another detail. By default, detail descriptions are automatically created for:

Detail descriptions can also be explicitly defined by adding them to DetailDescriptions collection of their parent DataGridCollectionView,  DataGridCollectionViewSource, or detail description.

Every detail description must have a unique, identifying relation name that can be provided through its RelationName property and that will be used by detail configurations to identify which description their configuration will be applied to. If the detail descriptions are automatically created, their relation name will be extracted from the underlying detail source or a default one will be provided. If they are explicitly provided, then their relation name must also be explicitly set.

Automatic creation of detail descriptions can be disabled by setting the AutoCreateDetailDescriptions property of the DataGridCollectionViewSource to false (by default, true) or by specifying so when creating an instance of the DataGridCollectionView. 

For each property in the corresponding detail description's source, a DataGridItemProperty will be created and added to its ItemProperties collection (you can consider these items to be the columns that will end up in the details). Each item-property object represents the characteristics of a property for an item in the detail description, including the DataType, Name, PropertyDescriptor, Title, and ValuePath. Automatic creation of item properties can be disabled by setting the AutoCreateItemProperties property of the DataGridCollectionViewSource to false (by default, true) or by specifying so when creating an instance of the DataGridCollectionView.

By default the Entity Framework does not load references to related entity objects. In this situation, the QueryDetails event exposed by the EntityDetailDescription class can be handled to provide details for a data item. For example, in the code snippet below, a query that will return the appropriate details for a parent item is executed and the Handled property set to true to indicate that the event was handled. In the case where the event is not handled and columns contain references to external Entity objects, the column would have remained empty unless those objects had been cached when loaded by some other means.

Private Sub EntityDetailDescription_QueryDetails( sender As Object, e As QueryEntityDetailsEventArgs )
  Dim customer As Customer = TryCast( e.ParentItem, Customer )
  ' Since EntityFramework doesn't load automatically references to
  ' other objects, we build a query that will include those objects.
  ' We start from the base query but we could have added restrictions
  ' to the query.
  Dim query As ObjectQuery( Of Order ) = customer.Orders.CreateSourceQuery()
  customer.Orders.Attach( query.Include( "Employee" ).Include( "Shipper" ) )
  e.Handled = True
End Sub

private void EntityDetailDescription_QueryDetails( object sender, QueryEntityDetailsEventArgs e )
{
 Customer customer = ( Customer )e.ParentItem;
 // Since EntityFramework doesn't load automatically references to
 // other objects, we build a query that will include those objects.
 // We start from the base query but we could have added restrictions
 // to the query.
 ObjectQuery<Order> query = customer.Orders.CreateSourceQuery();
 customer.Orders.Attach( query.Include( "Employee" ).Include( "Shipper" ) );
 e.Handled = true;
}

Because an Entity object does not have a default visual representation, its string representation will be displayed in the column. In order to change its appearance, a CellContentTemplate must be provided.

Grouping, Sorting, and Filtering

The data items that are to be displayed in a detail can be filtered through automatic filtering, which provides Excel-like end-user filtering according to the distinct values of each column (see Filtering Data).  

For more information on grouping, sorting, and filtering data items, refer to the Grouping Data, Sorting Data and Filtering Data topics.

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