3 steps to add JsonP endpoint for WCF service

1. Download Webservices.Jsonp.dll and add it as a reference to the WCF service project.
2. Add [WebGet] [JsonpBehavior] attributes to the WCF OperationContract functions.
   

       [ServiceContract]
       public interface ITestService
       {
           [OperationContract]
           string GetData(string input);
       }

       public class TestService : ITestService
       {
           [WebGet, JsonpBehavior]
           public string GetData(string input)
           {
               return string.Format("You entered: \"{0}\"", input);
           }
       }

3. Add JsonP endpoint for the service.
   

     <system.serviceModel>
       <services>
         <service behaviorConfiguration="WebServices.TestService.Service1Behavior"
           name="WebServices.TestService.TestService">
           <endpoint address="" binding="wsHttpBinding" contract="WebServices.TestService.ITestService">
           </endpoint>
           <endpoint address="jsonp" behaviorConfiguration="WebHttpEndpointBehavior" binding="customBinding"
                     bindingConfiguration="jsonpBinding" contract="WebServices.TestService.ITestService"/>
           <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
         </service>
       </services>
       <behaviors>
         <endpointBehaviors>
           <behavior name="WebHttpEndpointBehavior">
             <webHttp/>
             <enableWebScript/>
           </behavior>
         </endpointBehaviors>
         <serviceBehaviors>
           <behavior name="WebServices.TestService.Service1Behavior">
             <serviceMetadata httpGetEnabled="true"/>
             <serviceDebug includeExceptionDetailInFaults="true"/>
           </behavior>
         </serviceBehaviors>
       </behaviors>
       <bindings>
         <customBinding>
           <binding name="jsonpBinding">
             <jsonpMessageEncoding/>
             <httpTransport manualAddressing="true"/>
           </binding>
         </customBinding>
       </bindings>
       <extensions>
         <bindingElementExtensions>
           <add name="jsonpMessageEncoding" type="WebServices.JsonpBindingExtension, WebServices.Jsonp"/>
         </bindingElementExtensions>
       </extensions>
     </system.serviceModel>

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