The IMS LTI™ outcomes service allows consumers (such as Learning Management Systems) and providers (such as an online test) to send score information back and forth. Teachers love this! No more manually entering grades into the gradebook.

In this post, I show how to use my .NET LtiLibrary to add consumer outcomes support. My previous post, Quickly add LTI consumer functionality to your ASP.NET MVC web site, describes how to add the LtiLibrary project to your solution.

Add WebApi support to your web site

Use the Package Manager to add WebApi support to your web site project,

Then add a WebApiConfig class to the App_Start folder. If you already have one, be sure to enable the XmlSerializer (LTI outcomes use XML formatting),

using System.Web.Http;

namespace WebApplication1
{
   public static class WebApiConfig
   {
      public static void Register(HttpConfiguration config)
      {
         // Use XmlSerializer instead of DataContractSerializer
         config.Formatters.XmlFormatter.UseXmlSerializer = true;

         config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
            );
      }
   }
}

And finally, be sure to call WebApiConfig.Register when the web site starts,

using System.Web.Http;
using System.Web.Mvc;
using System.Web.Optimization;
using System.Web.Routing;

namespace WebApplication1
{
   public class MvcApplication : System.Web.HttpApplication
   {
      protected void Application_Start()
      {
         // This needs to appear before the non-api routes
         WebApiConfig.Register(GlobalConfiguration.Configuration);

         AreaRegistration.RegisterAllAreas();

         FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
         RouteConfig.RegisterRoutes(RouteTable.Routes);
         BundleConfig.RegisterBundles(BundleTable.Bundles);
      }
   }
}

Implement an OutcomesController

LtiLibrary contains an abstract OutcomesControllerBase with 4 methods that you need to override:

• GetConsumerSecrets – Return the list of secrets for the given OAuth consumer key. These will be used to validate the outcomes service call from the provider.
• DeleteResult – Delete the specified score.
• ReadResult – Read the specified score.
• ReplaceResult – Save the specific score.

Here is a simple example that works with the IMS LTI™ test tool,

using System.Collections.Generic;

namespace WebApplication1.Controllers
{
   public class OutcomesController : LtiLibrary.Consumer.OutcomesControllerBase
   {
      private static double? Score;

      protected override bool DeleteResult(LtiLibrary.Consumer.Result result)
      {
         Score = null;
         return true;
      }

      protected override IList<string> GetConsumerSecrets(string consumerKey)
      {
         return consumerKey.Equals("12345") ? new List<string> { "secret" } : new List<string>();
      }

      protected override bool ReadResult(LtiLibrary.Consumer.Result result)
      {
         result.DoubleValue = Score;
         return true;
      }

      protected override bool ReplaceResult(LtiLibrary.Consumer.Result result)
      {
         Score = result.DoubleValue;
         return true;
      }
   }
}

Tell the provider that you support outcomes

The last step is to tell the provider that you support outcomes. You do this by adding two values to the LTI request: the endpoint URL of the outcomes service, and the result ID which you can think of as the grade cell ID in the grade book. For example,

public ActionResult Launch()
{
   var request = new LtiLibrary.Consumer.LtiOutboundRequest
      {
         ConsumerKey = "12345",
         ConsumerSecret = "secret",
         ContextId = "1",
         ResourceLinkId = "1",
         Url = "http://www.imsglobal.org/developers/LTI/test/v1p1/tool.php"
      };

   // Add outcomes support
   var urlHelper = new UrlHelper(this.HttpContext.Request.RequestContext);
   var relativeUrl = urlHelper.HttpRouteUrl("DefaultApi", new { controller = "outcomes" });
   request.LisOutcomeServiceUrl = new Uri(this.HttpContext.Request.Url, relativeUrl).AbsoluteUri;
   request.LisResultSourcedId = "1";

   return View(request.GetLtiRequestModel());
}

Launch

If you launch the IMS LTI™ test tool, you will see a new option to test outcomes,

What’s Next?

Check out the sample Consumer in LTI Samples to see a more robust use of LtiLibrary. If you are a publisher, the sample Provider shows how to use LtiLibrary to handle LTI launch requests and even send grades back to the consumer.