OperationContractAttribute Class


Indicates that a method defines an operation that is part of a service contract in a Windows Communication Foundation (WCF) application.

Namespace:   System.ServiceModel
Assembly:  System.ServiceModel (in System.ServiceModel.dll)


public sealed class OperationContractAttribute : Attribute


Initializes a new instance of the OperationContractAttribute class.


Gets or sets the WS-Addressing action of the request message.


Indicates that an operation is implemented asynchronously using a Begin<methodName> and End<methodName> method pair in a service contract.


Gets a value that indicates whether the messages for this operation must be encrypted, signed, or both.


Gets or sets a value that indicates whether the method implements an operation that can initiate a session on the server (if such a session exists).


Gets or sets a value that indicates whether an operation returns a reply message.


Gets or sets a value that indicates whether the service operation causes the server to close the session after the reply message, if any, is sent.


Gets or sets the name of the operation.


Gets or sets a value that specifies whether the messages of an operation must be encrypted, signed, or both.


Gets or sets the value of the SOAP action for the reply message of the operation.


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


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.)


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


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.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.GetIDsOfNames(Guid, IntPtr, UInt32, UInt32, IntPtr)

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

System_CAPS_pubinterfaceSystem_CAPS_privmethod_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.)

System_CAPS_pubinterfaceSystem_CAPS_privmethod_Attribute.Invoke(UInt32, Guid, UInt32, Int16, IntPtr, IntPtr, IntPtr, IntPtr)

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

Apply the OperationContractAttribute to a method to indicate that the method implements a service operation as part of a service contract (specified by a ServiceContractAttribute attribute).

Use the OperationContractAttribute properties to control the structure of the operation and the values expressed in metadata:

  • The Action property specifies the action that uniquely identifies this operation. WCF dispatches request messages to methods based on their action.

  • The AsyncPattern property indicates that the operation is implemented or can be called asynchronously using a Begin/End method pair.

  • The HasProtectionLevel property indicates whether the ProtectionLevel property has been explicitly set.

  • The IsOneWay property indicates that the operation only consists of a single input message. The operation has no associated output message.

  • The IsInitiating property specifies whether this operation can be the initial operation in a session.

  • The IsTerminating property specifies whether WCF attempts to terminate the current session after the operation completes.

  • The ProtectionLevel property specifies the message-level security that an operation requires at run time.

  • The ReplyAction property specifies the action of the reply message for the operation.

The OperationContractAttribute attribute declares that a method is an operation in a service contract. Only methods attributed with the OperationContractAttribute are exposed as service operations. A service contract without any methods marked with the OperationContractAttribute exposes no operations.

The AsyncPattern property indicates that a pair of Begin<methodName> and End<methodName> methods form a single operation implemented asynchronously (whether on the client or the service). The ability of a service to implement operations asynchronously is a service implementation detail and is not exposed in metadata (such as Web Services Description Language (WSDL)).

Similarly, clients can choose to invoke operations asynchronously independent of how the service method is implemented. Calling service operations asynchronously in the client is recommended when a service method takes some time but must return information directly to the client. For details, see AsyncPattern.

The IsOneWay property indicates that a method does not return any value at all, including an empty underlying response message. This type of method is useful for notifications or event-style communication. Methods of this kind cannot return a reply message so the method's declaration must return void.


When programmatically retrieving the information store in this attribute, use the ContractDescription class instead of reflection.


If the IsOneWay property is set to false, (the default), even methods that return void are two-way methods at the underlying message level. In this case, the infrastructure creates and sends an empty message to indicate to the caller that the method has returned. Using this approach enables the application and the infrastructure to send error information (such as a SOAP fault) back to the client. Setting IsOneWay to true is the only way to prevent the creation and dispatch of a reply message. For more information, see One-Way Services.

The Action and ReplyAction properties can be used not only to modify the default action of SOAP messages but also to create handlers for unrecognized messages or to disable adding actions for direct message programming. Use the IsInitiating property to prevent clients from calling a particular service operation prior to other operations. Use the IsTerminating property to have WCF close the channel after clients call a particular service operation. For more information, see Using Sessions.

The ProtectionLevel property enables you to specify on the operation contract whether the operation messages are signed, encrypted, or signed and encrypted. If a binding cannot provide the security level required by the contract, an exception is thrown at run time. For more information, see ProtectionLevel and Understanding Protection Level.

Legacy Code Example

The following code example shows a simple service contract with one operation.

using System;
using System.Collections.Generic;
using System.Net.Security;
using System.ServiceModel;
using System.Text;

namespace Microsoft.WCF.Documentation
  public interface ISampleService{
    // This operation specifies an explicit protection level requirement.
    string SampleMethod(string msg);

  class SampleService : ISampleService
  #region ISampleService Members

  public string  SampleMethod(string msg)
    Console.WriteLine("Called with: {0}", msg);
 	  return "The service greets you: " + msg;


The following example is a service that implements an implicit service contract that specifies three operations. Two of the operations are two-way operations, which return underlying response messages to the caller no matter what the return value is. The third operation receives a call, an underlying inbound message, but returns no underlying response message.

public class OneAndTwoWay
  // The client waits until a response message appears.
  public int MethodOne (int x, out int y)
    y = 34;
    return 0;

  // The client waits until an empty response message appears.
  public void MethodTwo (int x)

  // The client returns as soon as an outbound message
  // is dispatched to the service; no response
  // message is generated or sent from the service.
  public void MethodThree (int x)

Universal Windows Platform
Available since 4.5
.NET Framework
Available since 3.0
Portable Class Library
Supported in: portable .NET platforms
Available since 2.0
Windows Phone Silverlight
Available since 7.0

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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