IPolicyExportExtension Interface (System.ServiceModel.Description)

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Microsoft Visual Studio 2008/.NET Framework 3.5

Other versions are also available for the following:

.NET Framework 3.0

.NET Framework Class Library

IPolicyExportExtension Interface

Implement IPolicyExportExtension to insert custom binding policy assertions in the Web Services Description Language (WSDL) information.

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

Syntax

Visual Basic (Declaration)

Public Interface IPolicyExportExtension

Visual Basic (Usage)

Dim instance As IPolicyExportExtension

public interface IPolicyExportExtension

Visual C++

public interface class IPolicyExportExtension

JScript

public interface IPolicyExportExtension

Remarks

Implement the IPolicyExportExtension interface on a System.ServiceModel.Channels..::.BindingElement object to write statements about endpoint capabilities or requirements into the WSDL information exposed by a particular endpoint. Typically the binding element is one that implements some feature, but this is not required. To load your policy exporter from a configuration file, implement a System.ServiceModel.Configuration..::.BindingElementExtensionElement that returns the policy exporter BindingElement object.

The policy exporter is used by Windows Communication Foundation (WCF) to use policy assertions to communicate to clients the existence of that custom binding requirement or endpoint capability.

The ExportPolicy method takes the MetadataExporter and PolicyConversionContext objects. Use the GetBindingAssertions, GetMessageBindingAssertions, and GetOperationBindingAssertions methods to obtain collections of policy assertions that have already been exported at various scopes. Then add your custom policy assertion object to the appropriate collection.

The Contract property exposes the ContractDescription for the endpoint that is being exported. This allows the IPolicyExportExtension extension to correctly scope their exported policy assertions. For example, security attributes in code may add behaviors to the ContractDescription that indicate where security policy assertions should be added.

The IPolicyExportExtension mechanism only supports exporting policy assertions in WSDL. To export custom WSDL elements you must use the IWsdlExportExtension mechanism to modify the WSDL directly.

Once custom policy assertions have been attached to the WSDL information, clients can detect and import the custom binding assertions by using an IPolicyImportExtension object.

Examples

The following code example shows the implementation of IPolicyExportExtension on a BindingElement. In this example, a custom binding element is attached to the WSDL file at the binding level.

#region IPolicyExporter Members
public void ExportPolicy(MetadataExporter exporter, PolicyConversionContext policyContext)
{
  if (exporter == null)
    throw new NullReferenceException("The MetadataExporter object passed to the ExporterBindingElement is null.");
  if (policyContext == null)
    throw new NullReferenceException("The PolicyConversionContext object passed to the ExporterBindingElement is null.");

  XmlElement elem = doc.CreateElement(name1, ns1);
  elem.InnerText = "My custom text.";
  XmlAttribute att = doc.CreateAttribute("MyCustomAttribute", ns1);
  att.Value = "ExampleValue";
  elem.Attributes.Append(att);
  XmlElement subElement = doc.CreateElement("MyCustomSubElement", ns1);
  subElement.InnerText = "Custom Subelement Text.";
  elem.AppendChild(subElement);
  policyContext.GetBindingAssertions().Add(elem);
  Console.WriteLine("The custom policy exporter was called.");
}
#endregion

The following code example shows a System.ServiceModel.Configuration..::.BindingElementExtensionElement implementation that enables the preceding policy exporter to be loaded from an application configuration file.

public class ExporterBindingElementConfigurationSection : BindingElementExtensionElement
{
  public ExporterBindingElementConfigurationSection()
  { Console.WriteLine("Exporter configuration section created."); }

  public override Type BindingElementType
  { get { return typeof(ExporterBindingElement); } }

  protected override BindingElement CreateBindingElement()
  { return new ExporterBindingElement(); }
}

The following example shows the host configuration file that loads the custom policy exporter.

<system.serviceModel>
  <services>
    <service 
      name="Microsoft.WCF.Documentation.StatefulService"
      behaviorConfiguration="addMetadata"
    >
      <host>
        <baseAddresses>
          <add baseAddress="http://localhost:8080/StatefulService"/>
        </baseAddresses>
      </host>
      <endpoint 
        address="http://localhost:8080/StatefulService" 
        binding="customBinding" 
        bindingConfiguration="exporter" 
        contract="Microsoft.WCF.Documentation.IStatefulService" 
      />
      <endpoint
        address="mex"
        binding="mexHttpBinding"
        contract="IMetadataExchange"
      />
    </service>
  </services>
  <behaviors>
    <serviceBehaviors>
      <behavior name="addMetadata">
        <serviceMetadata
           httpGetEnabled="true"
           httpGetUrl=""
         />
      </behavior>
    </serviceBehaviors>
  </behaviors>
  <bindings>
    <customBinding>
      <!-- 
        Use the name attribute of the binding element as 
        the value of the bindingConfiguration attribute in 
        your endpoint.
      -->
      <binding name ="exporter">
        <!-- Use the name attribute of your binding element extension specified below. -->
        <!-- Be certain the order of your custom binding elements is correct. -->
        <exporterBinding />
        <reliableSession/>
        <textMessageEncoding messageVersion="Default" />
        <httpTransport/>
      </binding>
    </customBinding>
  </bindings>
  <extensions>
    <bindingElementExtensions>
      <!-- Use the add element to associate your bindingelement configuration handler and give it a name to use. -->
      <add 
        type="Microsoft.WCF.Documentation.ExporterBindingElementConfigurationSection,PolicyExtensions" 
        name="exporterBinding" />
    </bindingElementExtensions>
  </extensions>
</system.serviceModel>

The following example shows the custom assertion in the WSDL file.

<wsdl:definitions xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:wsp="http://schemas.xmlsoap.org/ws/2004/09/policy"

  namespaces removed here for clarity...

>
  <wsp:Policy wsu:Id="CustomBinding_IStatefulService_policy">
    <wsp:ExactlyOne>
      <wsp:All>
        <acme 
          b:MyCustomAttribute="ExampleValue"
          xmlns="http://Microsoft/WCF/Documentation/CustomPolicyAssertions"           xmlns:b="http://Microsoft/WCF/Documentation/CustomPolicyAssertions">
           My custom text.
          <MyCustomSubElement>Custom Subelement Text.</MyCustomSubElement>
        </acme>
        <wsrm:RMAssertion xmlns:wsrm="http://schemas.xmlsoap.org/ws/2005/02/rm/policy">
          <wsrm:InactivityTimeout Milliseconds="600000" />
          <wsrm:AcknowledgementInterval Milliseconds="200" />
        </wsrm:RMAssertion>
        <wsaw:UsingAddressing />
      </wsp:All>
    </wsp:ExactlyOne>
  </wsp:Policy>
  <wsdl:import namespace="http://microsoft.wcf.documentation" location="" />

Platforms

Windows Vista, Windows XP SP2, 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.

Version Information

.NET Framework

Supported in: 3.5, 3.0

Reference

IPolicyExportExtension Members

System.ServiceModel.Description Namespace

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