Maps an inheritance hierarchy in a LINQ to SQL application.
Assembly: System.Data.Linq (in System.Data.Linq.dll)
Gets or sets the discriminator code value in a mapped inheritance hierarchy.
Gets or sets whether an object of this type in instantiated when the discriminator value does not match a specified value.
Gets or sets the type of the class in the hierarchy.
This API supports the product infrastructure and is not intended to be used directly from your code. Returns a value that indicates whether this instance is equal to a specified object.(Inherited from Attribute.)
Returns the hash code for this instance.(Inherited from Attribute.)
When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.(Inherited from Attribute.)
When overridden in a derived class, returns a value that indicates whether this instance equals a specified object.(Inherited from Attribute.)
Returns a string that represents the current object.(Inherited from Object.)
|_Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr)|
Maps a set of names to a corresponding set of dispatch identifiers.(Inherited from Attribute.)
|_Attribute.GetTypeInfo(UInt32, UInt32, IntPtr)|
Retrieves the type information for an object, which can be used to get the type information for an interface.(Inherited from Attribute.)
Retrieves the number of type information interfaces that an object provides (either 0 or 1).(Inherited from Attribute.)
|_Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr)|
Provides access to properties and methods exposed by an object.(Inherited from Attribute.)
Oneis 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
Available since 3.5
Windows Phone Silverlight
Available since 7.1
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.