Sep 212008

WCF never ceases to amaze me. Around every corner is another fascinating use for WCF, and much forethought on Microsoft’s part to make it look and behave great. I wanted to expose my services to my AJAX functions on my web site. I did not want to change my class library because it is used by other clients. I could just add the service classes to this web site, but why re-do when you can re-use.

If you have an existing WCF Service Library, you will need to expose it with the AspNetCompatibilityRequirementsMode.Allowed attribute on the service class to make it visible to ASP.NET clients. To avoid changing your service library in any way, the easiest thing to do is to add a new class to your web site that inherits from your service class. In this example, my existing service library uses the JeepServices namespace. Notice there is no implementation in this class. It is simply a placeholder for the real service implementation with the compatibility attribute attached.

    1 using System.ServiceModel;

    2 using System.ServiceModel.Activation;


    4 [ServiceBehavior]

    5 [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]

    6 public class WebHttpService : JeepServices.Service

    7 {

    8 }

Now that I have a ASP.NET compatible service, I need to expose it to the web site clients. Create a service file (.svc), and change the Service and CodeBehind attributes to point to the .svc file. The last thing you need is the Factory attribute. This notifies WCF of this service, eliminating the need for a configuration file entry for the service endpoint. In fact, you don’t even need the <system.servicemodel> in your configuration file at all. This is because it is only hosted as a web script, and cannot be called outside of the web site.

    1 <%@ ServiceHost Language=“C#” Debug=“true” Service=“WebHttpService” CodeBehind=“~/App_Code/WebHttpService.cs”

    2     Factory=“System.ServiceModel.Activation.WebScriptServiceHostFactory” %>


In your web page you will need a few things. First your will need a ScriptManager with a ServiceReference to the .svc file. You will then need the Javascript functions to make the call (DoJeepWork), handle the success message (OnJeepWorkSucceeded), and handle the failure message (OnJeepWorkFailed). Notice in DoJeepWork that you don’t call the service by it’s service name WebHttpService, you call it by the ServiceContract namespace and name. For this example, my interface has ServiceContract attributes Namespace = “JeepServices”, and Name = “JeepServiceContract”. Now you just wire up a ASP.NET control’s OnClientClick or an input or anchor tag’s onclick to DoJeepWork() and you are good to go.

    1 <%@ Page Language=“C#” AutoEventWireup=“true” CodeFile=“Default.aspx.cs” Inherits=“_Default” %>


    3 <!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN”

    4 “”>

    5 <html xmlns=“”>

    6 <head runat=“server”>

    7     <title>Test page</title>


    9     <script type=“text/javascript”>

   10         function DoJeepWork() {

   11             JeepServices.JeepServiceContract.DoWork(OnJeepWorkSuccedeed, OnJeepWorkFailed);

   12         }

   13         function OnJeepWorkSuccedeed(res) {

   14             document.getElementById(“<%= this.lblMessage.ClientID %>”).innerText = res;

   15         }

   16         function OnJeepWorkFailed(error) {

   17             // Alert user to the error.   

   18             alert(error.get_message());

   19         }

   20     </script>


   22 </head>

   23 <body>

   24     <form id=“form1” runat=“server”>

   25     <div>

   26         <asp:ScriptManager runat=“server”>

   27             <Services>

   28                 <asp:ServiceReference Path=“~/Services/WebHttpService.svc” InlineScript=“false” />

   29             </Services>

   30         </asp:ScriptManager>

   31         <asp:Label ID=“lblMessage” runat=“server” Text=“No work has been done” />

   32         <a href=“javascript:void(0); DoJeepWork()”>Do Work</a>

   33     </div>

   34     </form>

   35 </body>

   36 </html>


Mission accomplished! Here you’ve seen how to expose an existing WCF service library without changing any code in the library itself. Adding two files allowed the service to be exposed to your AJAX clients. Best of all, there is no configuration file changes to make.

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