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

    [ServiceContract(Namespace = "stc")]
    public interface IWorkflowDebugger
    {
        [OperationContract]
        string GetData(string str);
    }

    [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Required)]
    [ServiceBehavior(IncludeExceptionDetailInFaults = true)]
    public class WorkflowDebugger : IWorkflowDebugger
    {
     ...

string strCookie = Application.GetCookie(BrowserInteropHelper.Source);

HttpContext.Current.Request.Cookies