InheritanceMappingAttribute Class

Maps an inheritance hierarchy in a LINQ to SQL application.

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

[AttributeUsageAttribute(AttributeTargets.Class, AllowMultiple = true, Inherited = false)]
public sealed class InheritanceMappingAttribute : 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 IsDefault 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;
}

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 {  }

System.Object
  System.Attribute
    System.Data.Linq.Mapping.InheritanceMappingAttribute

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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.

.NET Framework

Supported in: 3.5
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