Add API help link to web api.

gistfile1.cs

protected async override System.Threading.Tasks.Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken)
        {
             var baseHandler = await base.SendAsync(request, cancellationToken);
             var content = await baseHandler.Content.ReadAsAsync<ResponseBase>();

             if (content != null)
             {
                 var apiDescription = request.GetActionDescriptor().Configuration.Services.GetApiExplorer().ApiDescriptions.Where(x => x.ActionDescriptor == request.GetActionDescriptor()).SingleOrDefault();

                 if (apiDescription != null)
                 {
                     var link = apiDescription.GetFriendlyId();
                     var returnLink =request.GetUrlHelper().Link("HelpPage_Default", new
                     {
                         action="api",
                         apiId = link
                     });
                     content.HelpLink = returnLink;
                 }


             }

             return baseHandler;
        }