unable access asp.net session in wcf service

Question

I am trying to access asp.net session in the WCF service. I am making jQuery AJAX calls from my asp.net application to wcf service. I have gone thru many SO questions and articles and tried everything they said but still i am not able access the client session in wcf service. When i write DataSet ds = HttpContext.Current.Session["data"] as DataSet; , ds is always null.

What am i missing here?

This is how my WCF service looks like: //Interface

[ServiceContract(SessionMode = SessionMode.Allowed)]
public interface IMyService
{
    [OperationContract(IsInitiating=true)]
    [WebInvoke(Method = "POST", BodyStyle = WebMessageBodyStyle.Wrapped, ResponseFormat = WebMessageFormat.Json, RequestFormat = WebMessageFormat.Json)]
    string GetData();

    [OperationContract]
    [WebInvoke(Method = "POST", BodyStyle = WebMessageBodyStyle.Wrapped, ResponseFormat = WebMessageFormat.Json, RequestFormat = WebMessageFormat.Json)]
    bool SaveData(string data);
}

//Service

[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Required)]
[ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]
public class MyService : IMyService
{
    public string GetData()
    {
        return "something";

    }
    public bool SaveData(string data)
    {
        DataSet ds = HttpContext.Current.Session["data"] as DataSet;
        return true;
    }

}

I am creating a dataset in the session_start of Global.asax and putting it in the session so that i can use it across the app as long as user session is valid.

    protected void Session_Start(object sender, EventArgs e)
    {
        DataSet ds = new DataSet();

        //Table to hold Product Selection
        DataTable dt = new DataTable("T1");
        dtSSNCertification.Columns.Add("Col1");
        ds.Tables.Add(dt);

        Session.Add("data", ds);
    }

This is how my wcf project's web.config bindings looks like:

  <service name="MyService">
    <endpoint address="" behaviorConfiguration="JSONPBehaviorConfiguration"
      binding="customBinding" bindingConfiguration="jsonpBinding"
      contract="IMyService">
    </endpoint>
  </service>

  <customBinding>
    <binding name="jsonpBinding" >
      <jsonpMessageEncoding />
      <httpTransport manualAddressing="true"/>
    </binding>
  </customBinding>


  <system.serviceModel>
    <serviceHostingEnvironment aspNetCompatibilityEnabled="true"/>
  </system.serviceModel>

Answer 1

To use ASP.NET features you need to enable ASP.NET Compatibility with WCF. In your web.config set this:

<system.serviceModel>
    <serviceHostingEnvironment aspNetCompatibilityEnabled="true">