InheritanceMappingAttribute Class
Maps an inheritance hierarchy in a LINQ to SQL application.
Assembly: System.Data.Linq (in System.Data.Linq.dll)
One InheritanceMappingAttribute is specified per mapped class.
Note the following when you map inheritance hierarchies:
All classes in a hierarchy must be mapped to a single table.
The table for an inheritance hierarchy must be declared on the mapped type that is at the top of the hierarchy. You cannot specify the table or mapping attributes in a class that is derived from the top class.
You can use an interface in a hierarchy, but LINQ does not map it.
You can skip a class in the hierarchy when you map classes, but you can query against mapped classes only.
For correct materialization, discriminator code values must be unique and match the values in the database. A row with a discriminator code value that does not exactly match (even by casing) instantiates the class by using IsDefault set to true.
This example shows inheritance mapping for a hierarchy where the top, mapped class (Shape) is abstract.
Public Enum ShapeType As Integer Square = 0 Circle = 1 End Enum <Table(Name:="Shape")> _ <InheritanceMapping(Code:=ShapeType.Square, Type:=GetType(Square), _ IsDefault:=True)> _ <InheritanceMapping(Code:=ShapeType.Circle, Type:=GetType(Circle))> _ Public MustInherit Class Shape <Column(IsDiscriminator:=True)> _ Public ShapeType As ShapeType = 0 End Class Public Class Square Inherits Shape <Column()> _ Public Side As Integer = 0 End Class Public Class Circle Inherits Shape <Column()> _ Public Radius As Integer = 0 End Class
The following example shows the inclusion of unmapped classes. You can put unmapped classes anywhere in the hierarchy.
' Unmapped and not queryable. Class A End Class ' Mapped and queryable. <Table()> _ <InheritanceMapping(Code:="B", Type:=GetType(B), _ IsDefault:=True)> _ <InheritanceMapping(Code:="D", Type:=GetType(D))> _ Class B Inherits A End Class ' Unmapped and not queryable. Class C Inherits B End Class ' Mapped and queryable. Class D Inherits C End Class ' Unmapped and not queryable. Class E Inherits D End Class
Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003
The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.