DataContractAttribute Class (System.Runtime.Serialization)

Other versions are also available for the following:

.NET Framework Class Library for Silverlight

DataContractAttribute Class

[This topic is pre-release documentation and is subject to change in future releases. Blank topics are included as placeholders.]

Specifies that the type defines or implements a data contract and can be serialized by a serializer, such as the DataContractSerializer.

Namespace: System.Runtime.Serialization
Assembly: System.Runtime.Serialization (in System.Runtime.Serialization.dll)

Syntax

Visual Basic (Declaration)

<AttributeUsageAttribute(AttributeTargets.Class Or AttributeTargets.Struct Or AttributeTargets.Enum, Inherited := False,  _
    AllowMultiple := False)> _
Public NotInheritable Class DataContractAttribute _
    Inherits Attribute

Visual Basic (Usage)

Dim instance As DataContractAttribute

[AttributeUsageAttribute(AttributeTargets.Class|AttributeTargets.Struct|AttributeTargets.Enum, Inherited = false, 
    AllowMultiple = false)]
public sealed class DataContractAttribute : Attribute

Visual C++

[AttributeUsageAttribute(AttributeTargets::Class|AttributeTargets::Struct|AttributeTargets::Enum, Inherited = false, 
    AllowMultiple = false)]
public ref class DataContractAttribute sealed : public Attribute

JScript

public final class DataContractAttribute extends Attribute

Remarks

Apply the DataContractAttribute attribute to types (classes, structures, or enumerations) that are used in serialization and deserialization operations by the DataContractSerializer. If you send or receive messages by using the Silverlight version 2 Beta 2 infrastructure, you can also apply the DataContractAttribute to any classes that hold and manipulate data sent in messages.

You should also apply the DataMemberAttribute to any field, property, or event that holds values you want to serialize. By applying the DataContractAttribute, you explicitly enable the DataContractSerializer to serialize and deserialize the data.

Silverlight 2 Beta 2 also supports a simplified opt-out model for serialization, where these attributes can be omitted from the type and the members of the type to be serialized. The data contract is implicit in the sense that the visibility modifiers (public, private) used by the type determines whether it and its members are included in the data contract. In this model, the name of a member is used to identify it in the serialized representation. A new IgnoreDataMemberAttribute attribute can be used to opt-out a member that is public when required.

Data Contracts

A data contract is an abstract description of a set of fields with a name and data type for each field. The data contract exists outside of any single implementation to allow services on different platforms to interoperate. As long as the data passed between the services conforms to the same contract, all the services can process the data. This processing is also known as a loosely coupled system. A data contract is also similar to an interface in that the contract specifies how data must be delivered so that it can be processed by an application. For example, the data contract might call for a data type named Person that has two text fields, named FirstName and LastName. To create a data contract, apply the DataContractAttribute to the class and apply the DataMemberAttribute to any fields or properties that must be serialized. When serialized, the data conforms to the data contract that is implicitly built into the type.

Note:
A data contract differs significantly from an actual interface in its inheritance behavior. Interfaces are inherited by any derived types. When you apply the DataContractAttribute to a base class, the derived types do not inherit the attribute or the behavior. However, if a derived type has a data contract, the data members of the base class are serialized. However, you must apply the DataMemberAttribute to new members in a derived class to make them serializable.

Note:

A data contract differs significantly from an actual interface in its inheritance behavior. Interfaces are inherited by any derived types. When you apply the DataContractAttribute to a base class, the derived types do not inherit the attribute or the behavior. However, if a derived type has a data contract, the data members of the base class are serialized. However, you must apply the DataMemberAttribute to new members in a derived class to make them serializable.

Reusing Existing Types

A data contract has two basic requirements:

A stable name.
A list of members.

The stable name consists of the namespace uniform resource identifier (URI) and the local name of the contract. By default, when you apply the DataContractAttribute to a class, it uses the class name as the local name and the class's namespace (prefixed with "http://schemas.datacontract.org/2004/07/") as the namespace URI. You can override the defaults by setting the Name and Namespace properties. You can also change the namespace by applying the ContractNamespaceAttribute to the namespace. Use this capability when you have an existing type that processes data exactly as you require but has a different namespace and class name from the data contract. By overriding the default values, you can reuse your existing type and have the serialized data conform to the data contract.