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How to: Create a Service with a Contract Interface

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The preferred way to create a Windows Communication Foundation (WCF) contract is by using an interface. This contract specifies the collection and structure of messages required to access the operations the service offers. This interface defines the input and output types by applying the ServiceContractAttribute class to the interface and the OperationContractAttribute class to the methods that you want to expose.

For more information about service contracts, see Designing Service Contracts.

Creating a WCF contract with an interface

  1. Create a new interface using Visual Basic, C#, or any other common language runtime language.

  2. Apply the ServiceContractAttribute class to the interface.

  3. Define the methods in the interface.

  4. Apply the OperationContractAttribute class to each method that must be exposed as part of the public WCF contract.

Example

The following code example shows an interface that defines a service contract.

using System.ServiceModel;

[ServiceContract]
public interface ICalculator
{
   [OperationContract]
   double Add(double n1, double n2);
   [OperationContract]
   double Subtract(double n1, double n2);
   [OperationContract]
   double Multiply(double n1, double n2);
   [OperationContract]
   double Divide(double n1, double n2);
}



<ServiceContract()> _
Public Interface ICalculator
    <OperationContract()> _
    Function Add(ByVal n1 As Double, ByVal n2 As Double) As Double
    <OperationContract()> _
    Function Subtract(ByVal n1 As Double, ByVal n2 As Double) As Double
    <OperationContract()> _
    Function Multiply(ByVal n1 As Double, ByVal n2 As Double) As Double
    <OperationContract()> _
    Function Divide(ByVal n1 As Double, ByVal n2 As Double) As Double
End Interface

The methods that have the OperationContractAttribute class applied use a request-reply message pattern by default. For more information about this message pattern, see How to: Create a Request-Reply Contract. You can also create and use other message patterns by setting properties of the attribute. For more examples, see How to: Create a One-Way Contract and How to: Create a Duplex Contract.

See also