Databases Reference
In-Depth Information
The
MetaForeignKeyColumn
class is a specialized descendant of the
MetaColumn
class that
represents many-to-one and one-to-one navigation properties, such as the
Supplier
prop-
erty of the Product entity in the Northwind data model. These “foreign key” columns in
the Dynamic Data metadata API have additional attributes that you can access through
this class.
public MetaTable ParentTable { get; }
The
ParentTable
property returns a
MetaTable
object describing the parent entity refer-
enced by the foreign key. In case of the
Supplier
property of the Product entity, the
ParentTable
property returns the
MetaTable
object describing the Supplier entity. This
property serves an important role in implementing filtering and navigation functionality.
In particular, it is used by the ForeignKey field and filter templates to retrieve the rows
from the parent table for display in a drop-down list.
public ReadOnlyCollection<string> ForeignKeyNames { get; }
The
ForeignKeyNames
property of the
MetaForeignKeyColumn
class returns a collection of
the primitive entity properties that form the foreign key. For the
Supplier
property of the
Product entity, this property returns a collection with a single column name—SupplierID.
The collection returned by this property has multiple items only if the parent table has a
compound primary key and the foreign key includes multiple primitive properties.
Presentation Logic
The remaining properties and methods of the
MetaForeignKeyColumn
class provide support
for implementing presentation logic in Dynamic Data applications.
public bool IsPrimaryKeyInThisTable { get; }
The
IsPrimaryKeyInThisTable
property of the
MetaForeignKeyColumn
class returns
true
if
any of the primitive components of the foreign key is a member of the primary key of the
entity itself. For example, the
Order_Detail
entity in the Northwind data model has a
compound primary key that consists of
OrderID
and
ProductID
properties. The
Order
navi-
gation property is represented by a
MetaForeignKeyColumn
whose
IsPrimaryKeyInThisTable
returns
true
because
OrderID
is a part of the primary key of the
Order_Detail
entity.
NOTE
Dynamic Data does not allow editing primary key values by default and uses the
IsPrimaryKeyInThisTableProperty
property to display read-only field templates for
foreign key columns that are a part of a primary key in Edit mode.
public IList<object> GetForeignKeyValues(object row);
