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How to: Expose a Contract to SOAP and Web Clients

By default, Windows Communication Foundation (WCF) makes endpoints available only to SOAP clients. In How to: Create a Basic WCF Web HTTP Service, an endpoint is made available to non-SOAP clients. There may be times when you want to make the same contract available both ways, as a Web endpoint and as a SOAP endpoint. This topic shows an example of how to do this.

To define the service contract

  1. Define a service contract using an interface marked with the ServiceContractAttribute, WebInvokeAttribute and the WebGetAttribute attributes, as shown in the following code.

    <ServiceContract()> _
    Public Interface IService
    
        <OperationContract()> _
        <WebGet()> _
        Function EchoWithGet(ByVal s As String) As String
    
        <OperationContract()> _
        <WebInvoke()> _
        Function EchoWithPost(ByVal s As String) As String
    End Interface
    
    
    Bb412196.note(en-us,VS.100).gifNote:
    By default WebInvokeAttribute maps POST calls to the operation. You can, however, specify the method to map to the operation by specifying a "method=" parameter. WebGetAttribute does not have a "method=" parameter and only maps GET calls to the service operation.

  2. Implement the service contract, as shown in the following code.

    Public Class Service
        Implements IService
        Public Function EchoWithGet(ByVal s As String) As String Implements IService.EchoWithGet
            Return "You said " + s
        End Function
    
        Public Function EchoWithPost(ByVal s As String) As String Implements IService.EchoWithPost
            Return "You said " + s
        End Function
    End Class
    
    

To host the service

  1. Create a ServiceHost object, as shown in the following code.

    Dim host As New ServiceHost(GetType(Service), New Uri("http://localhost:8000"))
    
    
  2. Add a ServiceEndpoint with BasicHttpBinding for the SOAP endpoint, as shown in the following code.

    host.AddServiceEndpoint(GetType(IService), New BasicHttpBinding(), "Soap")
    
    
  3. Add a ServiceEndpoint with WebHttpBinding for the non-SOAP endpoint and add the WebHttpBehavior to the endpoint, as shown in the following code.

    Dim endpoint As ServiceEndpoint
    endpoint = host.AddServiceEndpoint(GetType(IService), New WebHttpBinding(), "Web")
    endpoint.Behaviors.Add(New WebHttpBehavior())
    
    
  4. Call Open() on a ServiceHost instance to open the service host, as shown in the following code.

    host.Open()
    
    

To call service operations mapped to GET in Internet Explorer

  1. Open Internet Explorer and type "http://localhost:8000/Web/EchoWithGet?s=Hello, world!" and press ENTER. The URL contains the base address of the service ("http://localhost:8000/"), the relative address of the endpoint (""), the service operation to call ("EchoWithGet"), and a question mark followed by a list of named parameters separated by an ampersand (&).

To call service operations on the Web endpoint in code

  1. Create an instance of WebChannelFactory within a using block, as shown in the following code.

    Using wcf As New WebChannelFactory(Of IService)(New Uri("http://localhost:8000/Web"))
    
    
Bb412196.note(en-us,VS.100).gifNote:
Close() is automatically called on the channel at the end of the using block.

  1. Create the channel and call the service, as shown in the following code.

    Dim channel As IService = wcf.CreateChannel()
    
    Dim s As String
    
    Console.WriteLine("Calling EchoWithGet by HTTP GET: ")
    s = channel.EchoWithGet("Hello, world")
    Console.WriteLine("   Output:  {0}", s)
    
    Console.WriteLine("")
    Console.WriteLine("This can also be accomplished by navigating to")
    Console.WriteLine("http://localhost:8000/Web/EchoWithGet?s=Hello, world!")
    Console.WriteLine("in a web browser while this sample is running.")
    
    Console.WriteLine("")
    
    Console.WriteLine("Calling EchoWithPost by HTTP POST: ")
    s = channel.EchoWithPost("Hello, world")
    Console.WriteLine("   Output:  {0}", s)
    
    

To call service operations on the SOAP endpoint

  1. Create an instance of ChannelFactory within a using block, as shown in the following code.

    Using scf As New ChannelFactory(Of IService)(New BasicHttpBinding(), "http://localhost:8000/Soap")
    
    
  2. Create the channel and call the service, as shown in the following code.

    Dim channel As IService = scf.CreateChannel()
    
    Dim s As String
    
    Console.WriteLine("Calling EchoWithGet on SOAP endpoint: ")
    s = channel.EchoWithGet("Hello, world")
    Console.WriteLine("   Output:  {0}", s)
    
    Console.WriteLine("")
    
    Console.WriteLine("Calling EchoWithPost on SOAP endpoint: ")
    s = channel.EchoWithPost("Hello, world")
    Console.WriteLine("   Output:  {0}", s)
    
    

To close the service host

  1. Close the service host, as shown in the following code.

    host.Close()
    
    

Example

The following is the full code listing for this topic.

Imports System
Imports System.Collections.Generic
Imports System.ServiceModel
Imports System.ServiceModel.Description
Imports System.ServiceModel.Web
Imports System.Text

<ServiceContract()> _
Public Interface IService

    <OperationContract()> _
    <WebGet()> _
    Function EchoWithGet(ByVal s As String) As String

    <OperationContract()> _
    <WebInvoke()> _
    Function EchoWithPost(ByVal s As String) As String
End Interface

Public Class Service
    Implements IService
    Public Function EchoWithGet(ByVal s As String) As String Implements IService.EchoWithGet
        Return "You said " + s
    End Function

    Public Function EchoWithPost(ByVal s As String) As String Implements IService.EchoWithPost
        Return "You said " + s
    End Function
End Class
Module Program

    Sub Main()
        Dim host As New ServiceHost(GetType(Service), New Uri("http://localhost:8000"))
        host.AddServiceEndpoint(GetType(IService), New BasicHttpBinding(), "Soap")
        Dim endpoint As ServiceEndpoint
        endpoint = host.AddServiceEndpoint(GetType(IService), New WebHttpBinding(), "Web")
        endpoint.Behaviors.Add(New WebHttpBehavior())

        Try
            host.Open()

            Using wcf As New WebChannelFactory(Of IService)(New Uri("http://localhost:8000/Web"))

                Dim channel As IService = wcf.CreateChannel()

                Dim s As String

                Console.WriteLine("Calling EchoWithGet by HTTP GET: ")
                s = channel.EchoWithGet("Hello, world")
                Console.WriteLine("   Output:  {0}", s)

                Console.WriteLine("")
                Console.WriteLine("This can also be accomplished by navigating to")
                Console.WriteLine("http://localhost:8000/Web/EchoWithGet?s=Hello, world!")
                Console.WriteLine("in a web browser while this sample is running.")

                Console.WriteLine("")

                Console.WriteLine("Calling EchoWithPost by HTTP POST: ")
                s = channel.EchoWithPost("Hello, world")
                Console.WriteLine("   Output:  {0}", s)
                Console.WriteLine("")
            End Using
            Using scf As New ChannelFactory(Of IService)(New BasicHttpBinding(), "http://localhost:8000/Soap")

                Dim channel As IService = scf.CreateChannel()

                Dim s As String

                Console.WriteLine("Calling EchoWithGet on SOAP endpoint: ")
                s = channel.EchoWithGet("Hello, world")
                Console.WriteLine("   Output:  {0}", s)

                Console.WriteLine("")

                Console.WriteLine("Calling EchoWithPost on SOAP endpoint: ")
                s = channel.EchoWithPost("Hello, world")
                Console.WriteLine("   Output:  {0}", s)
                Console.WriteLine("")
            End Using


            Console.WriteLine("Press <Enter> to terminate")
            Console.ReadLine()
            host.Close()
        Catch cex As CommunicationException
            Console.WriteLine("An exception occurred:  {0}", cex.Message)
            host.Abort()
        End Try

    End Sub
End Module

Compiling the Code

When compiling Service.cs, reference System.ServiceModel.dll and System.ServiceModel.Web.dll.

See Also

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