fix example of using ASP.NET session

Author: Sergey Kanzhelev

articles/application-insights/app-insights-usage-send-user-context.md

@@ -16,26 +16,33 @@ ms.pm_owner: daviste;NumberByColors
 ms.author: daviste
 ---
 
-#  Send user context IDs to enable usage experiences in Azure Application Insights
+# Send user context IDs to enable usage experiences in Azure Application Insights
 
 ## Tracking users
 
-Application Insights enables you to monitor and track your users through a set of product usage tools: 
-* [Users, Sessions, Events](https://docs.microsoft.com/azure/application-insights/app-insights-usage-segmentation)
-* [Funnels](https://docs.microsoft.com/azure/application-insights/usage-funnels)
-* [Retention](https://docs.microsoft.com/azure/application-insights/app-insights-usage-retention)
-* Cohorts
-* [Workbooks](https://docs.microsoft.com/azure/application-insights/app-insights-usage-workbooks)
+Application Insights enables you to monitor and track your users through
+a set of product usage tools:
+
+- [Users, Sessions, Events](https://docs.microsoft.com/azure/application-insights/app-insights-usage-segmentation)
+- [Funnels](https://docs.microsoft.com/azure/application-insights/usage-funnels)
+- [Retention](https://docs.microsoft.com/azure/application-insights/app-insights-usage-retention)
+  Cohorts
+- [Workbooks](https://docs.microsoft.com/azure/application-insights/app-insights-usage-workbooks)
+
+In order to track what a user does over time, Application Insights needs
+an ID for each user or session. Include the following IDs in every
+custom event or page view.
 
-In order to track what a user does over time, Application Insights needs an ID for each user or session. Include the following IDs in every custom event or page view.
 - Users, Funnels, Retention, and Cohorts: Include user ID.
 - Sessions: Include session ID.
 
 If your app is integrated with the [JavaScript SDK](https://docs.microsoft.com/azure/application-insights/app-insights-javascript#set-up-application-insights-for-your-web-page), user ID is tracked automatically.
 
 ## Choosing user IDs
 
-User IDs should persist across user sessions to track how users behave over time. There are various approaches for persisting the ID.
+User IDs should persist across user sessions to track how users behave
+over time. There are various approaches for persisting the ID.
+
 - A definition of a user that you already have in your service.
 - If the service has access to a browser, it can pass the browser a cookie with an ID in it. The ID will persist for as long as the cookie remains in the user's browser.
 - If necessary, you can use a new ID each session, but the results about users will be limited. For example, you won't be able to see how a user's behavior changes over time.
@@ -46,50 +53,92 @@ If the ID contains personally identifying information about the user, it is not
 
 ## ASP.NET apps: Setting the user context in an ITelemetryInitializer
 
-Create a telemetry initializer, as described in detail [here](https://docs.microsoft.com/azure/application-insights/app-insights-api-filtering-sampling#add-properties-itelemetryinitializer), and set the Context.User.Id and the Context.Session.Id.
+Create a telemetry initializer, as described in detail [here](https://docs.microsoft.com/azure/application-insights/app-insights-api-filtering-sampling#add-properties-itelemetryinitializer). Pass the session ID through the request telemetry, and set the Context.User.Id and the Context.Session.Id.
 
 This example sets the user ID to an identifier that expires after the session. If possible, use a user ID that persists across sessions.
 
-```csharp
-
-    using System;
-    using System.Web;
-    using Microsoft.ApplicationInsights.Channel;
-    using Microsoft.ApplicationInsights.Extensibility;
+### Telemetry initializer
 
-    namespace MvcWebRole.Telemetry
+```csharp
+using System;
+using System.Web;
+using Microsoft.ApplicationInsights.Channel;
+using Microsoft.ApplicationInsights.Extensibility;
+
+namespace MvcWebRole.Telemetry
+{
+  /*
+   * Custom TelemetryInitializer that sets the user ID.
+   *
+   */
+  public class MyTelemetryInitializer : ITelemetryInitializer
+  {
+    public void Initialize(ITelemetry telemetry)
     {
-      /*
-       * Custom TelemetryInitializer that sets the user ID.
-       *
-       */
-      public class MyTelemetryInitializer : ITelemetryInitializer
-      {
-        public void Initialize(ITelemetry telemetry)
+        var ctx = HttpContext.Current;
+
+        // If telemetry initializer is called as part of request execution and not from some async thread
+        if (ctx != null)
         {
-            // For a full experience, track each user across sessions. For an incomplete view of user 
-            // behavior within a session, store user ID on the HttpContext Session.
-            // Set the user ID if we haven't done so yet.
-            if (HttpContext.Current.Session["UserId"] == null)
+            var requestTelemetry = ctx.GetRequestTelemetry();
+ 
+            // Set the user and session ids from requestTelemetry.Context.User.Id, which is populated in Application_PostAcquireRequestState in Global.asax.cs.
+            if (requestTelemetry != null && !string.IsNullOrEmpty(requestTelemetry.Context.User.Id) &&
+                (string.IsNullOrEmpty(telemetry.Context.User.Id) || string.IsNullOrEmpty(telemetry.Context.Session.Id)))
             {
-                HttpContext.Current.Session["UserId"] = Guid.NewGuid();
+                // Set the user id on the Application Insights telemetry item.
+                telemetry.Context.User.Id = requestTelemetry.Context.User.Id;
+ 
+                // Set the session id on the Application Insights telemetry item.
+                telemetry.Context.Session.Id = requestTelemetry.Context.User.Id;
             }
+        }
+    }
+  }
+}
+```
 
-            // Set the user id on the Application Insights telemetry item.
-            telemetry.Context.User.Id = (string)HttpContext.Current.Session["UserId"];
+### Global.asax.cs
 
-            // Set the session id on the Application Insights telemetry item.
-            telemetry.Context.Session.Id = HttpContext.Current.Session.SessionID;
+```csharp
+using System.Web;
+using System.Web.Http;
+using System.Web.Mvc;
+using System.Web.Optimization;
+using System.Web.Routing;
+
+namespace MvcWebRole.Telemetry
+{
+    public class MvcApplication : HttpApplication
+    {
+        protected void Application_Start()
+        {
+            AreaRegistration.RegisterAllAreas();
+            GlobalConfiguration.Configure(WebApiConfig.Register);
+            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
+            RouteConfig.RegisterRoutes(RouteTable.Routes);
+            BundleConfig.RegisterBundles(BundleTable.Bundles);
+        }
+ 
+        protected void Application_PostAcquireRequestState()
+        {
+            var requestTelemetry = Context.GetRequestTelemetry();
+ 
+            if (HttpContext.Current.Session != null && requestTelemetry != null && string.IsNullOrEmpty(requestTelemetry.Context.User.Id))
+            {
+                requestTelemetry.Context.User.Id = Session.SessionID;
+            }
         }
-      }
     }
+}
 ```
 
 ## Next steps
+
 - To enable usage experiences, start sending [custom events](https://docs.microsoft.com/azure/application-insights/app-insights-api-custom-events-metrics#trackevent) or [page views](https://docs.microsoft.com/azure/application-insights/app-insights-api-custom-events-metrics#page-views).
 - If you already send custom events or page views, explore the Usage tools to learn how users use your service.
-    * [Usage overview](app-insights-usage-overview.md)
-    * [Users, Sessions, and Events](app-insights-usage-segmentation.md)
-    * [Funnels](usage-funnels.md)
-    * [Retention](app-insights-usage-retention.md)
-    * [Workbooks](app-insights-usage-workbooks.md)
+    - [Usage overview](app-insights-usage-overview.md)
+    - [Users, Sessions, and Events](app-insights-usage-segmentation.md)
+    - [Funnels](usage-funnels.md)
+    - [Retention](app-insights-usage-retention.md)
+    - [Workbooks](app-insights-usage-workbooks.md)