InheritanceMappingAttribute Class
 
System_CAPS_noteNote

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Maps an inheritance hierarchy in a LINQ to SQL application.

Namespace:   System.Data.Linq.Mapping
Assembly:  System.Data.Linq (in System.Data.Linq.dll)

SystemObject
   SystemAttribute
    System.Data.Linq.MappingInheritanceMappingAttribute

[AttributeUsageAttribute(AttributeTargets.Class, AllowMultiple = true, 
	Inherited = false)]
public sealed class InheritanceMappingAttribute : Attribute
[AttributeUsageAttribute(AttributeTargets::Class, AllowMultiple = true, 
	Inherited = false)]
public ref class InheritanceMappingAttribute sealed : Attribute
[<Sealed>]
[<AttributeUsageAttribute(AttributeTargets.Class, AllowMultiple = true,
    Inherited = false)>]
type InheritanceMappingAttribute = 
    class
        inherit Attribute
    end
<AttributeUsageAttribute(AttributeTargets.Class, AllowMultiple := True,
	Inherited := False)>
Public NotInheritable Class InheritanceMappingAttribute
	Inherits Attribute
NameDescription
System_CAPS_pubmethod InheritanceMappingAttribute

Initializes a new instance of the InheritanceMappingAttribute class.

NameDescription
System_CAPS_pubproperty

Gets or sets the discriminator code value in a mapped inheritance hierarchy.

System_CAPS_pubproperty

Gets or sets whether an object of this type in instantiated when the discriminator value does not match a specified value.

System_CAPS_pubproperty

Gets or sets the type of the class in the hierarchy.

System_CAPS_pubproperty

When implemented in a derived class, gets a unique identifier for this Attribute.(Inherited from Attribute.)

NameDescription
System_CAPS_pubmethod Equals

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.)

System_CAPS_pubmethod GetHashCode

Returns the hash code for this instance.(Inherited from Attribute.)

System_CAPS_pubmethod GetType

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_pubmethod IsDefaultAttribute

When overridden in a derived class, indicates whether the value of this instance is the default value for the derived class.(Inherited from Attribute.)

System_CAPS_pubmethod Match

When overridden in a derived class, returns a value that indicates whether this instance equals a specified object.(Inherited from Attribute.)

System_CAPS_pubmethod ToString

Returns a string that represents the current object.(Inherited from Object.)

NameDescription
System_CAPS_pubinterface System_CAPS_privmethod _AttributeGetIDsOfNames

Maps a set of names to a corresponding set of dispatch identifiers.(Inherited from Attribute.)

System_CAPS_pubinterface System_CAPS_privmethod _AttributeGetTypeInfo

Retrieves the type information for an object, which can be used to get the type information for an interface.(Inherited from Attribute.)

System_CAPS_pubinterface System_CAPS_privmethod _AttributeGetTypeInfoCount

Retrieves the number of type information interfaces that an object provides (either 0 or 1).(Inherited from Attribute.)

System_CAPS_pubinterface System_CAPS_privmethod _AttributeInvoke

Provides access to properties and methods exposed by an object.(Inherited from Attribute.)

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 set to true.

This example shows inheritance mapping for a hierarchy where the top, mapped class (Shape) is abstract.

public enum ShapeType
{
    Square = 0, Circle = 1
}
[Table(Name = "Shape")]
[InheritanceMapping(Code = ShapeType.Square, Type = typeof(Square),
    IsDefault = true)]
[InheritanceMapping(Code = ShapeType.Circle, Type = typeof(Circle))]

abstract public class Shape
{
    [Column(IsDiscriminator = true)]
    public ShapeType ShapeType = 0;
}

public class Square : Shape
{
    [Column]
    public int Side = 0;
}
public class Circle : Shape
{
    [Column]
    public int Radius = 0;
}
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 {  }

// Mapped and queryable.
[Table]
[InheritanceMapping(Code = "B", Type = typeof(B), 
IsDefault = true)]
[InheritanceMapping(Code = "D", Type = typeof(D))]
class B: A {  }

// Unmapped and not queryable.
class C: B {  }

// Mapped and queryable.
class D: C {  }

// Unmapped and not queryable.
class E: D {  }
' 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
.NET Framework
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.

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