From a776a5ef601509c0e3b0cc3e3d7cb7fe599d909a Mon Sep 17 00:00:00 2001
From: Liudmila Molkova <lmolkova@microsoft.com>
Date: Tue, 19 Mar 2019 18:13:45 -0700
Subject: [PATCH 01/12] Remove DiagnosticAdapter and use DiagnosticListener
 directly

---
 .../HostingDiagnosticListener.cs              | 114 +++++++++++++++---
 .../IApplicationInsightDiagnosticListener.cs  |   6 +-
 .../Implementation/MvcDiagnosticsListener.cs  |  62 ++++++----
 .../Implementation/PropertyFetcher.cs         |  76 ++++++++++++
 .../Extensions/HttpRequestExtensions.cs       |   4 +-
 ...soft.ApplicationInsights.AspNetCore.csproj |   2 -
 .../RequestTrackingTelemetryModule.cs         |   2 +-
 .../OperationNameTelemetryInitializerTests.cs |  12 +-
 8 files changed, 226 insertions(+), 52 deletions(-)
 create mode 100644 src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/PropertyFetcher.cs

diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
index ae58fb36..2983d130 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
@@ -1,4 +1,6 @@
-namespace Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners
+using System.Collections.Generic;
+
+namespace Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners
 {
     using System;
     using System.Diagnostics;
@@ -7,6 +9,7 @@
     using System.Net.Http.Headers;
     using System.Text;
     using Extensibility.Implementation.Tracing;
+    using Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners.Implementation;
     using Microsoft.ApplicationInsights.AspNetCore.Extensions;
     using Microsoft.ApplicationInsights.Common;
     using Microsoft.ApplicationInsights.DataContracts;
@@ -14,7 +17,6 @@
     using Microsoft.ApplicationInsights.Extensibility.Implementation;
     using Microsoft.ApplicationInsights.Extensibility.W3C;
     using Microsoft.AspNetCore.Http;
-    using Microsoft.Extensions.DiagnosticAdapter;
     using Microsoft.Extensions.Primitives;
 
     /// <summary>
@@ -38,6 +40,24 @@ internal class HostingDiagnosticListener : IApplicationInsightDiagnosticListener
         private static readonly ActiveSubsciptionManager SubscriptionManager = new ActiveSubsciptionManager();
         private const string ActivityCreatedByHostingDiagnosticListener = "ActivityCreatedByHostingDiagnosticListener";
 
+        #region fetchers
+
+        // fetch is unique per event and per property
+        private readonly PropertyFetcher httpContextFetcherStart = new PropertyFetcher("HttpContext");
+        private readonly PropertyFetcher httpContextFetcherStop = new PropertyFetcher("HttpContext");
+        private readonly PropertyFetcher httpContextFetcherBeginRequest = new PropertyFetcher("httpContext");
+        private readonly PropertyFetcher httpContextFetcherEndRequest = new PropertyFetcher("httpContext");
+        private readonly PropertyFetcher httpContextFetcherDiagExceptionUnhandled = new PropertyFetcher("httpContext");
+        private readonly PropertyFetcher httpContextFetcherDiagExceptionHandled = new PropertyFetcher("httpContext");
+        private readonly PropertyFetcher httpContextFetcherHostingExceptionUnhandled = new PropertyFetcher("httpContext");
+        private readonly PropertyFetcher exceptionFetcherDiagExceptionUnhandled = new PropertyFetcher("exception");
+        private readonly PropertyFetcher exceptionFetcherDiagExceptionHandled = new PropertyFetcher("exception");
+        private readonly PropertyFetcher exceptionFetcherHostingExceptionUnhandled = new PropertyFetcher("exception");
+
+        private readonly PropertyFetcher timestampFetcherBeginRequest = new PropertyFetcher("timestamp");
+        private readonly PropertyFetcher timestampFetcherEndRequest = new PropertyFetcher("timestamp");
+        #endregion
+
         /// <summary>
         /// Initializes a new instance of the <see cref="T:HostingDiagnosticListener"/> class.
         /// </summary>
@@ -72,19 +92,9 @@ public void OnSubscribe()
         /// <inheritdoc/>
         public string ListenerName { get; } = "Microsoft.AspNetCore";
 
-        /// <summary>
-        /// Diagnostic event handler method for 'Microsoft.AspNetCore.Hosting.HttpRequestIn' event.
-        /// </summary>
-        [DiagnosticName("Microsoft.AspNetCore.Hosting.HttpRequestIn")]
-        public void OnHttpRequestIn()
-        {
-            // do nothing, just enable the diagnostic source
-        }
-
         /// <summary>
         /// Diagnostic event handler method for 'Microsoft.AspNetCore.Hosting.HttpRequestIn.Start' event.
         /// </summary>
-        [DiagnosticName("Microsoft.AspNetCore.Hosting.HttpRequestIn.Start")]
         public void OnHttpRequestInStart(HttpContext httpContext)
         {
             if (this.client.IsEnabled())
@@ -176,7 +186,6 @@ public void OnHttpRequestInStart(HttpContext httpContext)
         /// <summary>
         /// Diagnostic event handler method for 'Microsoft.AspNetCore.Hosting.HttpRequestIn.Stop' event.
         /// </summary>
-        [DiagnosticName("Microsoft.AspNetCore.Hosting.HttpRequestIn.Stop")]
         public void OnHttpRequestInStop(HttpContext httpContext)
         {
             EndRequest(httpContext, Stopwatch.GetTimestamp());
@@ -185,7 +194,6 @@ public void OnHttpRequestInStop(HttpContext httpContext)
         /// <summary>
         /// Diagnostic event handler method for 'Microsoft.AspNetCore.Hosting.BeginRequest' event.
         /// </summary>
-        [DiagnosticName("Microsoft.AspNetCore.Hosting.BeginRequest")]
         public void OnBeginRequest(HttpContext httpContext, long timestamp)
         {
             if (this.client.IsEnabled() && !this.enableNewDiagnosticEvents)
@@ -282,7 +290,6 @@ public void OnBeginRequest(HttpContext httpContext, long timestamp)
         /// <summary>
         /// Diagnostic event handler method for 'Microsoft.AspNetCore.Hosting.EndRequest' event.
         /// </summary>
-        [DiagnosticName("Microsoft.AspNetCore.Hosting.EndRequest")]
         public void OnEndRequest(HttpContext httpContext, long timestamp)
         {
             if (!this.enableNewDiagnosticEvents)
@@ -294,7 +301,6 @@ public void OnEndRequest(HttpContext httpContext, long timestamp)
         /// <summary>
         /// Diagnostic event handler method for 'Microsoft.AspNetCore.Hosting.UnhandledException' event.
         /// </summary>
-        [DiagnosticName("Microsoft.AspNetCore.Hosting.UnhandledException")]
         public void OnHostingException(HttpContext httpContext, Exception exception)
         {
             this.OnException(httpContext, exception);
@@ -310,7 +316,6 @@ public void OnHostingException(HttpContext httpContext, Exception exception)
         /// <summary>
         /// Diagnostic event handler method for 'Microsoft.AspNetCore.Hosting.HandledException' event.
         /// </summary>
-        [DiagnosticName("Microsoft.AspNetCore.Diagnostics.HandledException")]
         public void OnDiagnosticsHandledException(HttpContext httpContext, Exception exception)
         {
             this.OnException(httpContext, exception);
@@ -319,7 +324,6 @@ public void OnDiagnosticsHandledException(HttpContext httpContext, Exception exc
         /// <summary>
         /// Diagnostic event handler method for 'Microsoft.AspNetCore.Diagnostics.UnhandledException' event.
         /// </summary>
-        [DiagnosticName("Microsoft.AspNetCore.Diagnostics.UnhandledException")]
         public void OnDiagnosticsUnhandledException(HttpContext httpContext, Exception exception)
         {
             this.OnException(httpContext, exception);
@@ -559,5 +563,79 @@ public void Dispose()
         {
             SubscriptionManager.Detach(this);
         }
+
+        public void OnNext(KeyValuePair<string, object> value)
+        {
+            if (value.Key == "Microsoft.AspNetCore.Hosting.HttpRequestIn.Start")
+            {
+                if (this.httpContextFetcherStart.Fetch(value.Value) is HttpContext context)
+                {
+                    this.OnHttpRequestInStart(context);
+                }
+            }
+            else if (value.Key == "Microsoft.AspNetCore.Hosting.HttpRequestIn.Stop")
+            {
+                if (this.httpContextFetcherStop.Fetch(value.Value) is HttpContext context)
+                {
+                    this.OnHttpRequestInStop(context);
+                }
+            }
+            else if (value.Key == "Microsoft.AspNetCore.Hosting.BeginRequest")
+            {
+                var httpContext = this.httpContextFetcherBeginRequest.Fetch(value.Value) as HttpContext;
+                var timestamp = this.timestampFetcherBeginRequest.Fetch(value.Value) as long?;
+                if (httpContext != null && timestamp.HasValue)
+                {
+                    this.OnBeginRequest(httpContext, timestamp.Value);
+                }
+            }
+            else if (value.Key == "Microsoft.AspNetCore.Hosting.EndRequest")
+            {
+                var httpContext = this.httpContextFetcherEndRequest.Fetch(value.Value) as HttpContext;
+                var timestamp = this.timestampFetcherEndRequest.Fetch(value.Value) as long?;
+                if (httpContext != null && timestamp.HasValue)
+                {
+                    this.OnEndRequest(httpContext, timestamp.Value);
+                }
+            }
+            else if (value.Key == "Microsoft.AspNetCore.Diagnostics.UnhandledException")
+            {
+                var httpContext = this.httpContextFetcherDiagExceptionUnhandled.Fetch(value.Value) as HttpContext;
+                var exception = this.exceptionFetcherDiagExceptionUnhandled.Fetch(value.Value) as Exception;
+                if (httpContext != null && exception != null)
+                {
+                    this.OnDiagnosticsUnhandledException(httpContext, exception);
+                }
+            }
+            else if (value.Key == "Microsoft.AspNetCore.Diagnostics.HandledException")
+            {
+                var httpContext = this.httpContextFetcherDiagExceptionHandled.Fetch(value.Value) as HttpContext;
+                var exception = this.exceptionFetcherDiagExceptionHandled.Fetch(value.Value) as Exception;
+                if (httpContext != null && exception != null)
+                {
+                    this.OnDiagnosticsHandledException(httpContext, exception);
+                }
+            }
+            else if (value.Key == "Microsoft.AspNetCore.Hosting.UnhandledException")
+            {
+                var httpContext = this.httpContextFetcherHostingExceptionUnhandled.Fetch(value.Value) as HttpContext;
+                var exception = this.exceptionFetcherHostingExceptionUnhandled.Fetch(value.Value) as Exception;
+                if (httpContext != null && exception != null)
+                {
+                    this.OnHostingException(httpContext, exception);
+                }
+            }
+        }
+
+        /// <inheritdoc />
+        public void OnError(Exception error)
+        {
+        }
+
+        /// <inheritdoc />
+        public void OnCompleted()
+        {
+        }
+
     }
 }
\ No newline at end of file
diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/IApplicationInsightDiagnosticListener.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/IApplicationInsightDiagnosticListener.cs
index 95aec59f..97ed4b51 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/IApplicationInsightDiagnosticListener.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/IApplicationInsightDiagnosticListener.cs
@@ -1,11 +1,13 @@
-namespace Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners
+using System.Collections.Generic;
+
+namespace Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners
 {
     using System;
 
     /// <summary>
     /// Base diagnostic listener type for Application Insight
     /// </summary>
-    internal interface IApplicationInsightDiagnosticListener : IDisposable
+    internal interface IApplicationInsightDiagnosticListener : IDisposable, IObserver<KeyValuePair<string, object>>
     {
         /// <summary>
         /// Gets a value indicating which listener this instance should be subscribed to
diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/MvcDiagnosticsListener.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/MvcDiagnosticsListener.cs
index 81811608..70b5df30 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/MvcDiagnosticsListener.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/MvcDiagnosticsListener.cs
@@ -1,3 +1,5 @@
+using Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners.Implementation;
+
 namespace Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners
 {
     using System;
@@ -5,7 +7,6 @@ namespace Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners
     using System.Linq;
     using Microsoft.ApplicationInsights.DataContracts;
     using Microsoft.AspNetCore.Http;
-    using Microsoft.Extensions.DiagnosticAdapter;
 
     /// <summary>
     /// <see cref="IApplicationInsightDiagnosticListener"/> implementation that listens for evens specific to AspNetCore Mvc layer
@@ -15,17 +16,20 @@ public class MvcDiagnosticsListener : IApplicationInsightDiagnosticListener
         /// <inheritdoc />
         public string ListenerName { get; } = "Microsoft.AspNetCore";
 
+        private readonly  PropertyFetcher httpContextFetcher = new PropertyFetcher("httpContext");
+        private readonly PropertyFetcher routeDataFetcher = new PropertyFetcher("routeData");
+        private readonly PropertyFetcher routeValuesFetcher = new PropertyFetcher("Values");
+
         /// <summary>
         /// Diagnostic event handler method for 'Microsoft.AspNetCore.Mvc.BeforeAction' event
         /// </summary>
-        [DiagnosticName("Microsoft.AspNetCore.Mvc.BeforeAction")]
-        public void OnBeforeAction(HttpContext httpContext, IRouteData routeData)
+        public void OnBeforeAction(HttpContext httpContext, IDictionary<string, object> routeValues)
         {
             var telemetry = httpContext.Features.Get<RequestTelemetry>();
 
             if (telemetry != null && string.IsNullOrEmpty(telemetry.Name))
             {
-                string name = this.GetNameFromRouteContext(routeData);
+                string name = this.GetNameFromRouteContext(routeValues);
 
                 if (!string.IsNullOrEmpty(name))
                 {
@@ -35,19 +39,12 @@ public void OnBeforeAction(HttpContext httpContext, IRouteData routeData)
             }
         }
 
-        /// <inheritdoc />
-        public void OnSubscribe()
-        {
-        }
-
-        private string GetNameFromRouteContext(IRouteData routeData)
+        private string GetNameFromRouteContext(IDictionary<string, object> routeValues)
         {
             string name = null;
 
-            if (routeData.Values.Count > 0)
+            if (routeValues.Count > 0)
             {
-                var routeValues = routeData.Values;
-
                 object controller;
                 routeValues.TryGetValue("controller", out controller);
                 string controllerString = (controller == null) ? string.Empty : controller.ToString();
@@ -98,19 +95,40 @@ private string GetNameFromRouteContext(IRouteData routeData)
             return name;
         }
 
-        public void Dispose()
+        /// <inheritdoc />
+        public void OnSubscribe()
         {
         }
 
-        /// <summary>
-        /// Proxy interface for <c>RouteData</c> class from Microsoft.AspNetCore.Routing.Abstractions
-        /// </summary>
-        public interface IRouteData
+        /// <inheritdoc />
+        public void OnNext(KeyValuePair<string, object> value)
+        {
+            if (value.Key == "Microsoft.AspNetCore.Mvc.BeforeAction")
+            {
+                var context = httpContextFetcher.Fetch(value.Value) as HttpContext;
+                var routeData = routeDataFetcher.Fetch(value.Value);
+                var routeValues = routeValuesFetcher.Fetch(routeData) as IDictionary<string, object>;
+
+                if (context != null && routeValues != null)
+                {
+                    this.OnBeforeAction(context, routeValues);
+                }
+            }
+        }
+
+        /// <inheritdoc />
+        public void OnError(Exception error)
+        {
+        }
+
+        /// <inheritdoc />
+        public void OnCompleted()
+        {
+        }
+
+        /// <inheritdoc />
+        public void Dispose()
         {
-            /// <summary>
-            /// Gets the set of values produced by routes on the current routing path.
-            /// </summary>
-            IDictionary<string, object> Values { get; }
         }
     }
 }
\ No newline at end of file
diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/PropertyFetcher.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/PropertyFetcher.cs
new file mode 100644
index 00000000..a234138d
--- /dev/null
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/PropertyFetcher.cs
@@ -0,0 +1,76 @@
+namespace Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners.Implementation
+{
+    using System;
+    using System.Reflection;
+
+    // see https://github.com/dotnet/corefx/blob/master/src/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/DiagnosticSourceEventSource.cs
+    /// <summary>
+    /// Efficient implementation of fetching properties of anonymous types with reflection.
+    /// </summary>
+    internal class PropertyFetcher
+    {
+        private readonly string propertyName;
+        private PropertyFetch innerFetcher;
+
+        public PropertyFetcher(string propertyName)
+        {
+            this.propertyName = propertyName;
+        }
+
+        public object Fetch(object obj)
+        {
+            if (this.innerFetcher == null)
+            {
+                this.innerFetcher = PropertyFetch.FetcherForProperty(obj.GetType().GetTypeInfo().GetDeclaredProperty(this.propertyName));
+            }
+
+            return this.innerFetcher?.Fetch(obj);
+        }
+
+        private class PropertyFetch
+        {
+            /// <summary>
+            /// Create a property fetcher from a .NET Reflection PropertyInfo class that
+            /// represents a property of a particular type.  
+            /// </summary>
+            public static PropertyFetch FetcherForProperty(PropertyInfo propertyInfo)
+            {
+                if (propertyInfo == null)
+                {
+                    // returns null on any fetch.
+                    return new PropertyFetch();
+                }
+
+                var typedPropertyFetcher = typeof(TypedFetchProperty<,>);
+                var instantiatedTypedPropertyFetcher = typedPropertyFetcher.GetTypeInfo().MakeGenericType(
+                    propertyInfo.DeclaringType, propertyInfo.PropertyType);
+                return (PropertyFetch)Activator.CreateInstance(instantiatedTypedPropertyFetcher, propertyInfo);
+            }
+
+            /// <summary>
+            /// Given an object, fetch the property that this propertyFetch represents. 
+            /// </summary>
+            public virtual object Fetch(object obj)
+            {
+                return null;
+            }
+
+            private class TypedFetchProperty<TObject, TProperty> : PropertyFetch
+            {
+                private readonly Func<TObject, TProperty> propertyFetch;
+
+                public TypedFetchProperty(PropertyInfo property)
+                {
+                    this.propertyFetch =
+                        (Func<TObject, TProperty>)
+                        property.GetMethod.CreateDelegate(typeof(Func<TObject, TProperty>));
+                }
+
+                public override object Fetch(object obj)
+                {
+                    return this.propertyFetch((TObject)obj);
+                }
+            }
+        }
+    }
+}
diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/Extensions/HttpRequestExtensions.cs b/src/Microsoft.ApplicationInsights.AspNetCore/Extensions/HttpRequestExtensions.cs
index 66479425..a5b0fd18 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/Extensions/HttpRequestExtensions.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/Extensions/HttpRequestExtensions.cs
@@ -1,4 +1,6 @@
-namespace Microsoft.ApplicationInsights.AspNetCore.Extensions
+using Microsoft.AspNetCore.Http.Extensions;
+
+namespace Microsoft.ApplicationInsights.AspNetCore.Extensions
 {
     using System;
     using System.Text;
diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/Microsoft.ApplicationInsights.AspNetCore.csproj b/src/Microsoft.ApplicationInsights.AspNetCore/Microsoft.ApplicationInsights.AspNetCore.csproj
index afa21aea..07f3488d 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/Microsoft.ApplicationInsights.AspNetCore.csproj
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/Microsoft.ApplicationInsights.AspNetCore.csproj
@@ -89,7 +89,6 @@
     <PackageReference Include="Microsoft.AspNetCore.Hosting" Version="1.0.2" />
     <PackageReference Include="Microsoft.Extensions.Configuration" Version="1.0.2" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="1.0.2" />
-    <PackageReference Include="Microsoft.Extensions.DiagnosticAdapter" Version="1.1.0" />
     <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="1.0.2" />
     <PackageReference Include="System.Text.Encodings.Web" Version="4.3.1" />
   </ItemGroup>
@@ -97,7 +96,6 @@
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
   <PackageReference Include="Microsoft.Extensions.Configuration" Version="2.0.0" />
   <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="2.0.0" />
-  <PackageReference Include="Microsoft.Extensions.DiagnosticAdapter" Version="2.0.0" />
   <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="2.0.0" />
   <PackageReference Include="System.Text.Encodings.Web" Version="4.3.1" />
   </ItemGroup>
diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/RequestTrackingTelemetryModule.cs b/src/Microsoft.ApplicationInsights.AspNetCore/RequestTrackingTelemetryModule.cs
index fb3e3313..088c2d03 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/RequestTrackingTelemetryModule.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/RequestTrackingTelemetryModule.cs
@@ -105,7 +105,7 @@ void IObserver<DiagnosticListener>.OnNext(DiagnosticListener value)
             {
                 if (applicationInsightDiagnosticListener.ListenerName == value.Name)
                 {
-                    subs.Add(value.SubscribeWithAdapter(applicationInsightDiagnosticListener));
+                    subs.Add(value.Subscribe(applicationInsightDiagnosticListener));
                     applicationInsightDiagnosticListener.OnSubscribe();
                 }
             }
diff --git a/test/Microsoft.ApplicationInsights.AspNetCore.Tests/TelemetryInitializers/OperationNameTelemetryInitializerTests.cs b/test/Microsoft.ApplicationInsights.AspNetCore.Tests/TelemetryInitializers/OperationNameTelemetryInitializerTests.cs
index 10fd3927..27d25e65 100644
--- a/test/Microsoft.ApplicationInsights.AspNetCore.Tests/TelemetryInitializers/OperationNameTelemetryInitializerTests.cs
+++ b/test/Microsoft.ApplicationInsights.AspNetCore.Tests/TelemetryInitializers/OperationNameTelemetryInitializerTests.cs
@@ -86,7 +86,7 @@ public void InitializeSetsTelemetryOperationNameToControllerFromActionContext()
 
             var telemetryListener = new DiagnosticListener(TestListenerName);
             var initializer = new MvcDiagnosticsListener();
-            telemetryListener.SubscribeWithAdapter(initializer);
+            telemetryListener.Subscribe(initializer);
             telemetryListener.Write("Microsoft.AspNetCore.Mvc.BeforeAction",
                 new { httpContext = contextAccessor.HttpContext, routeData = actionContext.RouteData });
 
@@ -107,7 +107,7 @@ public void InitializeSetsTelemetryOperationNameToControllerAndActionFromActionC
 
             var telemetryListener = new DiagnosticListener(TestListenerName);
             var initializer = new MvcDiagnosticsListener();
-            telemetryListener.SubscribeWithAdapter(initializer);
+            telemetryListener.Subscribe(initializer);
             telemetryListener.Write("Microsoft.AspNetCore.Mvc.BeforeAction",
                 new { httpContext = contextAccessor.HttpContext, routeData = actionContext.RouteData });
 
@@ -127,7 +127,7 @@ public void InitializeSetsTelemetryOperationNameToPageFromActionContext()
 
             var telemetryListener = new DiagnosticListener(TestListenerName);
             var initializer = new MvcDiagnosticsListener();
-            telemetryListener.SubscribeWithAdapter(initializer);
+            telemetryListener.Subscribe(initializer);
             telemetryListener.Write("Microsoft.AspNetCore.Mvc.BeforeAction",
                 new { httpContext = contextAccessor.HttpContext, routeData = actionContext.RouteData });
 
@@ -149,7 +149,7 @@ public void InitializeSetsTelemetryOperationNameToControllerAndActionAndParamete
 
             var telemetryListener = new DiagnosticListener(TestListenerName);
             var initializer = new MvcDiagnosticsListener();
-            telemetryListener.SubscribeWithAdapter(initializer);
+            telemetryListener.Subscribe(initializer);
             telemetryListener.Write("Microsoft.AspNetCore.Mvc.BeforeAction",
                 new { httpContext = contextAccessor.HttpContext, routeData = actionContext.RouteData });
 
@@ -173,7 +173,7 @@ public void InitializeSortsParameters()
 
             var telemetryListener = new DiagnosticListener(TestListenerName);
             var initializer = new MvcDiagnosticsListener();
-            telemetryListener.SubscribeWithAdapter(initializer);
+            telemetryListener.Subscribe(initializer);
             telemetryListener.Write("Microsoft.AspNetCore.Mvc.BeforeAction",
                 new { httpContext = contextAccessor.HttpContext, routeData = actionContext.RouteData });
 
@@ -194,7 +194,7 @@ public void InitializeDoesNotIncludeRouteGroupKeyInParametersList()
             var contextAccessor = HttpContextAccessorHelper.CreateHttpContextAccessor(new RequestTelemetry(), actionContext);
             var telemetryListener = new DiagnosticListener(TestListenerName);
             var initializer = new MvcDiagnosticsListener();
-            telemetryListener.SubscribeWithAdapter(initializer);
+            telemetryListener.Subscribe(initializer);
             telemetryListener.Write("Microsoft.AspNetCore.Mvc.BeforeAction",
                 new { httpContext = contextAccessor.HttpContext, routeData = actionContext.RouteData });
 

From 82f492c9bb494cb80963a32c4d3bc54fa1a33de1 Mon Sep 17 00:00:00 2001
From: Liudmila Molkova <lmolkova@microsoft.com>
Date: Tue, 19 Mar 2019 18:17:49 -0700
Subject: [PATCH 02/12] minor fixes

---
 .../Implementation/HostingDiagnosticListener.cs              | 5 ++---
 .../Implementation/MvcDiagnosticsListener.cs                 | 3 +--
 .../Extensions/HttpRequestExtensions.cs                      | 4 +---
 3 files changed, 4 insertions(+), 8 deletions(-)

diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
index 2983d130..65b5a238 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
@@ -1,8 +1,7 @@
-using System.Collections.Generic;
-
-namespace Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners
+namespace Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners
 {
     using System;
+    using System.Collections.Generic;
     using System.Diagnostics;
     using System.Globalization;
     using System.Linq;
diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/MvcDiagnosticsListener.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/MvcDiagnosticsListener.cs
index 70b5df30..48c25853 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/MvcDiagnosticsListener.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/MvcDiagnosticsListener.cs
@@ -1,10 +1,9 @@
-using Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners.Implementation;
-
 namespace Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners
 {
     using System;
     using System.Collections.Generic;
     using System.Linq;
+    using Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners.Implementation;
     using Microsoft.ApplicationInsights.DataContracts;
     using Microsoft.AspNetCore.Http;
 
diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/Extensions/HttpRequestExtensions.cs b/src/Microsoft.ApplicationInsights.AspNetCore/Extensions/HttpRequestExtensions.cs
index a5b0fd18..66479425 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/Extensions/HttpRequestExtensions.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/Extensions/HttpRequestExtensions.cs
@@ -1,6 +1,4 @@
-using Microsoft.AspNetCore.Http.Extensions;
-
-namespace Microsoft.ApplicationInsights.AspNetCore.Extensions
+namespace Microsoft.ApplicationInsights.AspNetCore.Extensions
 {
     using System;
     using System.Text;

From 44e550e6e411925129c5725a4e666a2af51e6551 Mon Sep 17 00:00:00 2001
From: Liudmila Molkova <lmolkova@microsoft.com>
Date: Wed, 20 Mar 2019 11:36:51 -0700
Subject: [PATCH 03/12] switch

---
 .../HostingDiagnosticListener.cs              | 116 +++++++++---------
 .../IApplicationInsightDiagnosticListener.cs  |   5 +-
 2 files changed, 61 insertions(+), 60 deletions(-)

diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
index 65b5a238..f90b2d27 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
@@ -565,64 +565,66 @@ public void Dispose()
 
         public void OnNext(KeyValuePair<string, object> value)
         {
-            if (value.Key == "Microsoft.AspNetCore.Hosting.HttpRequestIn.Start")
-            {
-                if (this.httpContextFetcherStart.Fetch(value.Value) is HttpContext context)
-                {
-                    this.OnHttpRequestInStart(context);
-                }
-            }
-            else if (value.Key == "Microsoft.AspNetCore.Hosting.HttpRequestIn.Stop")
-            {
-                if (this.httpContextFetcherStop.Fetch(value.Value) is HttpContext context)
-                {
-                    this.OnHttpRequestInStop(context);
-                }
-            }
-            else if (value.Key == "Microsoft.AspNetCore.Hosting.BeginRequest")
-            {
-                var httpContext = this.httpContextFetcherBeginRequest.Fetch(value.Value) as HttpContext;
-                var timestamp = this.timestampFetcherBeginRequest.Fetch(value.Value) as long?;
-                if (httpContext != null && timestamp.HasValue)
-                {
-                    this.OnBeginRequest(httpContext, timestamp.Value);
-                }
-            }
-            else if (value.Key == "Microsoft.AspNetCore.Hosting.EndRequest")
-            {
-                var httpContext = this.httpContextFetcherEndRequest.Fetch(value.Value) as HttpContext;
-                var timestamp = this.timestampFetcherEndRequest.Fetch(value.Value) as long?;
-                if (httpContext != null && timestamp.HasValue)
-                {
-                    this.OnEndRequest(httpContext, timestamp.Value);
-                }
-            }
-            else if (value.Key == "Microsoft.AspNetCore.Diagnostics.UnhandledException")
-            {
-                var httpContext = this.httpContextFetcherDiagExceptionUnhandled.Fetch(value.Value) as HttpContext;
-                var exception = this.exceptionFetcherDiagExceptionUnhandled.Fetch(value.Value) as Exception;
-                if (httpContext != null && exception != null)
-                {
-                    this.OnDiagnosticsUnhandledException(httpContext, exception);
-                }
-            }
-            else if (value.Key == "Microsoft.AspNetCore.Diagnostics.HandledException")
-            {
-                var httpContext = this.httpContextFetcherDiagExceptionHandled.Fetch(value.Value) as HttpContext;
-                var exception = this.exceptionFetcherDiagExceptionHandled.Fetch(value.Value) as Exception;
-                if (httpContext != null && exception != null)
-                {
-                    this.OnDiagnosticsHandledException(httpContext, exception);
-                }
-            }
-            else if (value.Key == "Microsoft.AspNetCore.Hosting.UnhandledException")
+            HttpContext httpContext = null;
+            Exception exception = null;
+            long? timestamp = null;
+
+            switch (value.Key)
             {
-                var httpContext = this.httpContextFetcherHostingExceptionUnhandled.Fetch(value.Value) as HttpContext;
-                var exception = this.exceptionFetcherHostingExceptionUnhandled.Fetch(value.Value) as Exception;
-                if (httpContext != null && exception != null)
-                {
-                    this.OnHostingException(httpContext, exception);
-                }
+                case "Microsoft.AspNetCore.Hosting.HttpRequestIn.Start":
+                    httpContext = this.httpContextFetcherStart.Fetch(value.Value) as HttpContext;
+                    if (httpContext != null)
+                    {
+                        this.OnHttpRequestInStart(httpContext);
+                    }
+                    break;
+                case "Microsoft.AspNetCore.Hosting.HttpRequestIn.Stop":
+                    httpContext = this.httpContextFetcherStop.Fetch(value.Value) as HttpContext;
+                    if (httpContext != null)
+                    {
+                        this.OnHttpRequestInStop(httpContext);
+                    }
+                    break;
+                case "Microsoft.AspNetCore.Hosting.BeginRequest":
+                    httpContext = this.httpContextFetcherBeginRequest.Fetch(value.Value) as HttpContext;
+                    timestamp = this.timestampFetcherBeginRequest.Fetch(value.Value) as long?;
+                    if (httpContext != null && timestamp.HasValue)
+                    {
+                        this.OnBeginRequest(httpContext, timestamp.Value);
+                    }
+                    break;
+                case "Microsoft.AspNetCore.Hosting.EndRequest":
+                    httpContext = this.httpContextFetcherEndRequest.Fetch(value.Value) as HttpContext;
+                    timestamp = this.timestampFetcherEndRequest.Fetch(value.Value) as long?;
+                    if (httpContext != null && timestamp.HasValue)
+                    {
+                        this.OnEndRequest(httpContext, timestamp.Value);
+                    }
+                    break;
+                case "Microsoft.AspNetCore.Diagnostics.UnhandledException":
+                    httpContext = this.httpContextFetcherDiagExceptionUnhandled.Fetch(value.Value) as HttpContext;
+                    exception = this.exceptionFetcherDiagExceptionUnhandled.Fetch(value.Value) as Exception;
+                    if (httpContext != null && exception != null)
+                    {
+                        this.OnDiagnosticsUnhandledException(httpContext, exception);
+                    }
+                    break;
+                case "Microsoft.AspNetCore.Diagnostics.HandledException":
+                    httpContext = this.httpContextFetcherDiagExceptionHandled.Fetch(value.Value) as HttpContext;
+                    exception = this.exceptionFetcherDiagExceptionHandled.Fetch(value.Value) as Exception;
+                    if (httpContext != null && exception != null)
+                    {
+                        this.OnDiagnosticsHandledException(httpContext, exception);
+                    }
+                    break;
+                case "Microsoft.AspNetCore.Hosting.UnhandledException":
+                    httpContext = this.httpContextFetcherHostingExceptionUnhandled.Fetch(value.Value) as HttpContext;
+                    exception = this.exceptionFetcherHostingExceptionUnhandled.Fetch(value.Value) as Exception;
+                    if (httpContext != null && exception != null)
+                    {
+                        this.OnHostingException(httpContext, exception);
+                    }
+                    break;
             }
         }
 
diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/IApplicationInsightDiagnosticListener.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/IApplicationInsightDiagnosticListener.cs
index 97ed4b51..6714874e 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/IApplicationInsightDiagnosticListener.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/IApplicationInsightDiagnosticListener.cs
@@ -1,8 +1,7 @@
-using System.Collections.Generic;
-
-namespace Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners
+namespace Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners
 {
     using System;
+    using System.Collections.Generic;
 
     /// <summary>
     /// Base diagnostic listener type for Application Insight

From ac85c0cb47c131ffbefcda6488fa5000956a7b34 Mon Sep 17 00:00:00 2001
From: Dmitry-Matveev <d.g.matveev@gmail.com>
Date: Wed, 20 Mar 2019 16:55:42 -0700
Subject: [PATCH 04/12] Initialize IKey

---
 .../Implementation/HostingDiagnosticListener.cs               | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
index ae58fb36..b9b74ef8 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
@@ -343,7 +343,7 @@ private RequestTelemetry InitializeRequestTelemetry(HttpContext httpContext, Act
                 }
             }
 
-            this.client.Initialize(requestTelemetry);
+            this.client.InitializeInstrumentationKey(requestTelemetry);
 
             requestTelemetry.Source = GetAppIdFromRequestHeader(httpContext.Request.Headers, requestTelemetry.Context.InstrumentationKey);
 
@@ -363,7 +363,7 @@ private string GetAppIdFromRequestHeader(IHeaderDictionary requestHeaders, strin
             {
                 headerCorrelationId = StringUtilities.EnforceMaxLength(headerCorrelationId, InjectionGuardConstants.AppIdMaxLength);
                 if (string.IsNullOrEmpty(instrumentationKey))
-                {
+                {In
                     return headerCorrelationId;
                 }
 

From bf33cad2ae3ebe8251eae451caae068df66c0b5f Mon Sep 17 00:00:00 2001
From: Dmitry-Matveev <d.g.matveev@gmail.com>
Date: Wed, 20 Mar 2019 17:02:00 -0700
Subject: [PATCH 05/12] Fix typo

---
 .../Implementation/HostingDiagnosticListener.cs                 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
index 9bc7dad1..d25dc7b2 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
@@ -366,7 +366,7 @@ private string GetAppIdFromRequestHeader(IHeaderDictionary requestHeaders, strin
             {
                 headerCorrelationId = StringUtilities.EnforceMaxLength(headerCorrelationId, InjectionGuardConstants.AppIdMaxLength);
                 if (string.IsNullOrEmpty(instrumentationKey))
-                {In
+                {
                     return headerCorrelationId;
                 }
 

From 328778008289ea9af72b496dbea5c9cff214b704 Mon Sep 17 00:00:00 2001
From: Dmitry-Matveev <d.g.matveev@gmail.com>
Date: Fri, 29 Mar 2019 17:45:20 -0700
Subject: [PATCH 06/12] GetUri with Concat

---
 .../Extensions/HttpRequestExtensions.cs       | 24 ++++---------------
 1 file changed, 5 insertions(+), 19 deletions(-)

diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/Extensions/HttpRequestExtensions.cs b/src/Microsoft.ApplicationInsights.AspNetCore/Extensions/HttpRequestExtensions.cs
index 66479425..1230e15a 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/Extensions/HttpRequestExtensions.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/Extensions/HttpRequestExtensions.cs
@@ -28,26 +28,12 @@ public static Uri GetUri(this HttpRequest request)
             {
                 throw new ArgumentException("Http request Scheme is not specified");
             }
-
-            string hostName = request.Host.HasValue ? request.Host.ToString() : UnknownHostName;
             
-            var builder = new StringBuilder();
-
-            builder.Append(request.Scheme)
-                .Append("://")
-                .Append(hostName);
-
-            if (true == request.Path.HasValue)
-            {
-                builder.Append(request.Path.Value);
-            }
-
-            if (true == request.QueryString.HasValue)
-            {
-                builder.Append(request.QueryString);
-            }
-
-            return new Uri(builder.ToString());
+            return new Uri(string.Concat(request.Scheme,
+                    "://",
+                    request.Host.HasValue ? request.Host.Value : UnknownHostName,
+                    request.Path.HasValue ? request.Path.Value : "",
+                    request.QueryString.HasValue ? request.QueryString.Value : ""));
         }
     }
 }

From 2e3f01a405c00c8c4dce8204e4dfa3e0d01995ad Mon Sep 17 00:00:00 2001
From: Dmitry-Matveev <d.g.matveev@gmail.com>
Date: Tue, 9 Apr 2019 16:48:05 -0700
Subject: [PATCH 07/12] Set Header fixes, use Properties for AspNetCoreEnv.

---
 .../Implementation/HeadersUtilities.cs        | 24 ++++++++++++++++++-
 .../Implementation/HttpHeadersUtilities.cs    |  2 +-
 ...pNetCoreEnvironmentTelemetryInitializer.cs |  6 ++---
 3 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HeadersUtilities.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HeadersUtilities.cs
index a10865af..658d7a3e 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HeadersUtilities.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HeadersUtilities.cs
@@ -5,6 +5,7 @@ namespace Microsoft.ApplicationInsights.AspNetCore.DiagnosticListeners
     using System.Linq;
     using System.Text.RegularExpressions;
     using Microsoft.ApplicationInsights.Common;
+    using Microsoft.Extensions.Primitives;
 
     /// <summary>
     /// Generic functions that can be used to get and set Http headers.
@@ -20,7 +21,7 @@ internal static class HeadersUtilities
         public static string GetHeaderKeyValue(IEnumerable<string> headerValues, string keyName)
         {
             if (headerValues != null)
-            {
+            {                
                 foreach (string keyNameValue in headerValues)
                 {
                     string[] keyNameValueParts = keyNameValue.Trim().Split('=');
@@ -56,6 +57,27 @@ public static IEnumerable<string> SetHeaderKeyValue(IEnumerable<string> headerVa
                     .Concat(newHeaderKeyValue);
         }
 
+        internal static StringValues SetHeaderKeyValue(string[] currentHeaders, string key, string value)
+        {
+            if (currentHeaders != null)
+            {
+                for (int index = 0; index < currentHeaders.Length; index++)
+                {
+                    if (HeaderMatchesKey(currentHeaders[index], key))
+                    {
+                        currentHeaders[index] = string.Concat(key, "=", value);
+                        return currentHeaders;
+                    }
+                }
+
+                return StringValues.Concat(currentHeaders, string.Concat(key, "=", value));                
+            }
+            else
+            {
+                return string.Concat(key, "=", value);
+            }
+        }
+
         /// <summary>
         /// Check if the header contains the key, case insensitve, ignore leading and trailing whitepsaces.
         /// </summary>
diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HttpHeadersUtilities.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HttpHeadersUtilities.cs
index 4a8bc3ea..0dff7bc7 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HttpHeadersUtilities.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HttpHeadersUtilities.cs
@@ -94,7 +94,7 @@ internal static void SetHeaderKeyValue(IHeaderDictionary headers, string headerN
                 throw new ArgumentNullException(nameof(headers));
             }
 
-            headers[headerName] = new StringValues(HeadersUtilities.SetHeaderKeyValue(headers[headerName].AsEnumerable(), keyName, keyValue).ToArray());
+            headers[headerName] = HeadersUtilities.SetHeaderKeyValue(headers[headerName], keyName, keyValue);
         }
 
         internal static string[] SafeGetCommaSeparatedHeaderValues(IHeaderDictionary headers, string headerName, int maxLength, int maxItems)
diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/TelemetryInitializers/AspNetCoreEnvironmentTelemetryInitializer.cs b/src/Microsoft.ApplicationInsights.AspNetCore/TelemetryInitializers/AspNetCoreEnvironmentTelemetryInitializer.cs
index c42565d3..1867aec2 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/TelemetryInitializers/AspNetCoreEnvironmentTelemetryInitializer.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/TelemetryInitializers/AspNetCoreEnvironmentTelemetryInitializer.cs
@@ -23,10 +23,10 @@ public AspNetCoreEnvironmentTelemetryInitializer(IHostingEnvironment environment
 
         /// <inheritdoc />
         public void Initialize(ITelemetry telemetry)
-        {
-            if (environment != null && !telemetry.Context.GlobalProperties.ContainsKey(AspNetCoreEnvironmentPropertyName))
+        {   
+            if (environment != null && !telemetry.Context.Properties.ContainsKey(AspNetCoreEnvironmentPropertyName))
             {
-                telemetry.Context.GlobalProperties.Add(AspNetCoreEnvironmentPropertyName, environment.EnvironmentName);
+                telemetry.Context.Properties.Add(AspNetCoreEnvironmentPropertyName, environment.EnvironmentName);
             }
         }
     }

From a3fd4932411fbab198b2bb3213f32effe74ea4b3 Mon Sep 17 00:00:00 2001
From: Dmitry-Matveev <d.g.matveev@gmail.com>
Date: Wed, 10 Apr 2019 15:21:04 -0700
Subject: [PATCH 08/12] SetHeader fixes

---
 .../Implementation/HeadersUtilities.cs        | 12 +-------
 .../Implementation/HttpHeadersUtilities.cs    | 17 -----------
 .../HeadersUtilitiesTest.cs                   | 28 +++++++++----------
 3 files changed, 14 insertions(+), 43 deletions(-)

diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HeadersUtilities.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HeadersUtilities.cs
index 658d7a3e..2794f9d4 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HeadersUtilities.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HeadersUtilities.cs
@@ -39,7 +39,7 @@ public static string GetHeaderKeyValue(IEnumerable<string> headerValues, string
         /// <summary>
         /// Given the provided list of header value strings, return a comma-separated list of key
         /// name/value pairs with the provided keyName and keyValue. If the initial header value
-        /// strings contains the key name, then the original key value should be replaced with the
+        /// string contains the key name, then the original key value should be replaced with the
         /// provided key value. If the initial header value strings don't contain the key name,
         /// then the key name/value pair should be added to the comma-separated list and returned.
         /// </summary>
@@ -47,16 +47,6 @@ public static string GetHeaderKeyValue(IEnumerable<string> headerValues, string
         /// <param name="keyName">The name of the key to add.</param>
         /// <param name="keyValue">The value of the key to add.</param>
         /// <returns>The result of setting the provided key name/value pair into the provided headerValues.</returns>
-        public static IEnumerable<string> SetHeaderKeyValue(IEnumerable<string> headerValues, string keyName, string keyValue)
-        {
-            string[] newHeaderKeyValue = new[] { string.Format(CultureInfo.InvariantCulture, "{0}={1}", keyName.Trim(), keyValue.Trim()) };
-            return headerValues == null || !headerValues.Any()
-                ? newHeaderKeyValue
-                : headerValues
-                    .Where(headerValue => !HeaderMatchesKey(headerValue, keyName))
-                    .Concat(newHeaderKeyValue);
-        }
-
         internal static StringValues SetHeaderKeyValue(string[] currentHeaders, string key, string value)
         {
             if (currentHeaders != null)
diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HttpHeadersUtilities.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HttpHeadersUtilities.cs
index 0dff7bc7..d1002896 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HttpHeadersUtilities.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HttpHeadersUtilities.cs
@@ -65,28 +65,11 @@ internal static bool ContainsRequestContextKeyValue(IHeaderDictionary headers, s
             return !string.IsNullOrEmpty(GetHeaderKeyValue(headers, RequestResponseHeaders.RequestContextHeader, keyName));
         }
 
-        internal static void SetRequestContextKeyValue(HttpHeaders headers, string keyName, string keyValue)
-        {
-            SetHeaderKeyValue(headers, RequestResponseHeaders.RequestContextHeader, keyName, keyValue);
-        }
-
         internal static void SetRequestContextKeyValue(IHeaderDictionary headers, string keyName, string keyValue)
         {
             SetHeaderKeyValue(headers, RequestResponseHeaders.RequestContextHeader, keyName, keyValue);
         }
 
-        internal static void SetHeaderKeyValue(HttpHeaders headers, string headerName, string keyName, string keyValue)
-        {
-            if (headers == null)
-            {
-                throw new ArgumentNullException(nameof(headers));
-            }
-
-            IEnumerable<string> headerValues = GetHeaderValues(headers, headerName);
-            headers.Remove(headerName);
-            headers.Add(headerName, HeadersUtilities.SetHeaderKeyValue(headerValues, keyName, keyValue));
-        }
-
         internal static void SetHeaderKeyValue(IHeaderDictionary headers, string headerName, string keyName, string keyValue)
         {
             if (headers == null)
diff --git a/test/Microsoft.ApplicationInsights.AspNetCore.Tests/HeadersUtilitiesTest.cs b/test/Microsoft.ApplicationInsights.AspNetCore.Tests/HeadersUtilitiesTest.cs
index a771b0aa..2a6c63fd 100644
--- a/test/Microsoft.ApplicationInsights.AspNetCore.Tests/HeadersUtilitiesTest.cs
+++ b/test/Microsoft.ApplicationInsights.AspNetCore.Tests/HeadersUtilitiesTest.cs
@@ -1,7 +1,6 @@
 namespace Microsoft.ApplicationInsights.AspNetCore.Tests
 {
     using System.Collections.Generic;
-    using System.Linq;
     using DiagnosticListeners;
     using Xunit;
 
@@ -30,36 +29,35 @@ public void ShouldReturnNullWhenKeyNotExists()
         [Fact]
         public void ShouldReturnHeadersWhenNoHeaderValues()
         {
-            IEnumerable<string> newHeaders = HeadersUtilities.SetHeaderKeyValue(null, "Key", "Value");
+            string[] newHeaders = HeadersUtilities.SetHeaderKeyValue(null, "Key", "Value");
 
             Assert.NotNull(newHeaders);
-            Assert.Equal(1, newHeaders.Count());
-            Assert.Equal("Key=Value", newHeaders.First());
+            Assert.Single(newHeaders);
+            Assert.Equal("Key=Value", newHeaders[0]);
         }
 
         [Fact]
         public void ShouldAppendHeaders()
         {
-            IEnumerable<string> existing = new List<string>() { "ExistKey=ExistValue" };
-            IEnumerable<string> result = HeadersUtilities.SetHeaderKeyValue(existing, "NewKey", "NewValue");
+            string[] existing = new string[] { "ExistKey=ExistValue" };
+            string[] result = HeadersUtilities.SetHeaderKeyValue(existing, "NewKey", "NewValue");
 
             Assert.NotNull(result);
-            Assert.Equal(2, result.Count());
-            Assert.NotNull(result.FirstOrDefault(headerValue => headerValue.Equals("ExistKey=ExistValue")));
-            Assert.NotNull(result.FirstOrDefault(headerValue => headerValue.Equals("NewKey=NewValue")));
+            Assert.Equal(2, result.Length);
+            Assert.Equal("ExistKey=ExistValue", result[0]);
+            Assert.Equal("NewKey=NewValue", result[0]);
         }
 
         [Fact]
         public void ShouldUpdateExistingHeader()
         {
-            IEnumerable<string> existing = new List<string>() { "ExistKey=ExistValue", "NoiseKey=NoiseValue" };
-            IEnumerable<string> result = HeadersUtilities.SetHeaderKeyValue(existing, "ExistKey", "NewValue");
+            string[] existing = new string[] { "ExistKey=ExistValue", "NoiseKey=NoiseValue" };
+            string[] result = HeadersUtilities.SetHeaderKeyValue(existing, "ExistKey", "NewValue");
 
             Assert.NotNull(result);
-            Assert.Equal(2, result.Count());
-            Assert.Null(result.FirstOrDefault(headerValue => headerValue.Equals("ExistKey=ExistValue")));
-            Assert.NotNull(result.FirstOrDefault(headerValue => headerValue.Equals("ExistKey=NewValue")));
-            Assert.NotNull(result.FirstOrDefault(headerValue => headerValue.Equals("NoiseKey=NoiseValue")));
+            Assert.Equal(2, result.Length);
+            Assert.Equal("ExistKey=NewValue", result[0]);
+            Assert.Equal("NoiseKey=NoiseValue", result[0]);
         }
     }
 }

From c039272df9d4ea77e952f5905018cb4040164a11 Mon Sep 17 00:00:00 2001
From: Dmitry-Matveev <d.g.matveev@gmail.com>
Date: Wed, 10 Apr 2019 16:24:17 -0700
Subject: [PATCH 09/12] Test Fixes - 1

---
 .../HeadersUtilitiesTest.cs                                 | 4 ++--
 .../AspNetCoreEnvironmentTelemetryInitializerTests.cs       | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/test/Microsoft.ApplicationInsights.AspNetCore.Tests/HeadersUtilitiesTest.cs b/test/Microsoft.ApplicationInsights.AspNetCore.Tests/HeadersUtilitiesTest.cs
index 2a6c63fd..fe066f8b 100644
--- a/test/Microsoft.ApplicationInsights.AspNetCore.Tests/HeadersUtilitiesTest.cs
+++ b/test/Microsoft.ApplicationInsights.AspNetCore.Tests/HeadersUtilitiesTest.cs
@@ -45,7 +45,7 @@ public void ShouldAppendHeaders()
             Assert.NotNull(result);
             Assert.Equal(2, result.Length);
             Assert.Equal("ExistKey=ExistValue", result[0]);
-            Assert.Equal("NewKey=NewValue", result[0]);
+            Assert.Equal("NewKey=NewValue", result[1]);
         }
 
         [Fact]
@@ -57,7 +57,7 @@ public void ShouldUpdateExistingHeader()
             Assert.NotNull(result);
             Assert.Equal(2, result.Length);
             Assert.Equal("ExistKey=NewValue", result[0]);
-            Assert.Equal("NoiseKey=NoiseValue", result[0]);
+            Assert.Equal("NoiseKey=NoiseValue", result[1]);
         }
     }
 }
diff --git a/test/Microsoft.ApplicationInsights.AspNetCore.Tests/TelemetryInitializers/AspNetCoreEnvironmentTelemetryInitializerTests.cs b/test/Microsoft.ApplicationInsights.AspNetCore.Tests/TelemetryInitializers/AspNetCoreEnvironmentTelemetryInitializerTests.cs
index 783199dc..7fa681fd 100644
--- a/test/Microsoft.ApplicationInsights.AspNetCore.Tests/TelemetryInitializers/AspNetCoreEnvironmentTelemetryInitializerTests.cs
+++ b/test/Microsoft.ApplicationInsights.AspNetCore.Tests/TelemetryInitializers/AspNetCoreEnvironmentTelemetryInitializerTests.cs
@@ -19,10 +19,10 @@ public void InitializeDoesNotOverrideExistingProperty()
         {
             var initializer = new AspNetCoreEnvironmentTelemetryInitializer(new HostingEnvironment() { EnvironmentName = "Production"});
             var telemetry = new RequestTelemetry();
-            telemetry.Context.GlobalProperties.Add("AspNetCoreEnvironment", "Development");
+            telemetry.Context.Properties.Add("AspNetCoreEnvironment", "Development");
             initializer.Initialize(telemetry);
 
-            Assert.Equal("Development", telemetry.Context.GlobalProperties["AspNetCoreEnvironment"]);
+            Assert.Equal("Development", telemetry.Context.Properties["AspNetCoreEnvironment"]);
         }
 
         [Fact]
@@ -32,7 +32,7 @@ public void InitializeSetsCurrentEnvironmentNameToProperty()
             var telemetry = new RequestTelemetry();
             initializer.Initialize(telemetry);
 
-            Assert.Equal("Production", telemetry.Context.GlobalProperties["AspNetCoreEnvironment"]);
+            Assert.Equal("Production", telemetry.Context.Properties["AspNetCoreEnvironment"]);
         }
     }
 }

From 03d7d25f184503d211c3abdd7ffad77252fc774d Mon Sep 17 00:00:00 2001
From: Liudmila Molkova <lmolkova@microsoft.com>
Date: Wed, 10 Apr 2019 19:06:46 -0700
Subject: [PATCH 10/12] fix tests

---
 .../HostingDiagnosticListener.cs              | 34 ++++++++++++++-----
 .../HostingDiagnosticListenerTest.cs          |  4 ---
 2 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
index d25dc7b2..d0081195 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HostingDiagnosticListener.cs
@@ -161,7 +161,15 @@ public void OnHttpRequestInStart(HttpContext httpContext)
                     // with W3C support on .NET https://github.com/dotnet/corefx/issues/30331
 
                     newActivity = new Activity(ActivityCreatedByHostingDiagnosticListener);
-                    newActivity.SetParentId(StringUtilities.GenerateTraceId());
+                    if (this.enableW3CHeaders)
+                    {
+                        newActivity.GenerateW3CContext();
+                        newActivity.SetParentId(newActivity.GetTraceId());
+                    }
+                    else
+                    {
+                        newActivity.SetParentId(W3CUtilities.GenerateTraceId());
+                    }
                     // end of workaround
                 }
 
@@ -257,7 +265,9 @@ public void OnBeginRequest(HttpContext httpContext, long timestamp)
                             InjectionGuardConstants.RequestHeaderMaxLength);
                     }
                 }
-                else if(!activity.IsW3CActivity())
+
+                // no headers
+                else if (originalParentId == null)
                 {
                     // As a first step in supporting W3C protocol in ApplicationInsights,
                     // we want to generate Activity Ids in the W3C compatible format.
@@ -266,8 +276,16 @@ public void OnBeginRequest(HttpContext httpContext, long timestamp)
                     // So if there is no current Activity (i.e. there were no Request-Id header in the incoming request), we'll override ParentId on 
                     // the current Activity by the properly formatted one. This workaround should go away
                     // with W3C support on .NET https://github.com/dotnet/corefx/issues/30331
-                    
-                    activity.SetParentId(StringUtilities.GenerateTraceId());
+
+                    if (this.enableW3CHeaders)
+                    {
+                        activity.GenerateW3CContext();
+                        activity.SetParentId(activity.GetTraceId());
+                    }
+                    else
+                    {
+                        activity.SetParentId(W3CUtilities.GenerateTraceId());
+                    }
 
                     // end of workaround
                 }
@@ -337,6 +355,10 @@ private RequestTelemetry InitializeRequestTelemetry(HttpContext httpContext, Act
                 requestTelemetry.Context.Operation.Id = activity.RootId;
                 requestTelemetry.Id = activity.Id;
             }
+            else
+            {
+                activity.UpdateTelemetry(requestTelemetry, false);
+            }
 
             foreach (var prop in activity.Baggage)
             {
@@ -490,10 +512,6 @@ private void SetW3CContext(IHeaderDictionary requestHeaders, Activity activity,
                     InjectionGuardConstants.TraceParentHeaderMaxLength);
                 activity.SetTraceparent(parentTraceParent);
             }
-            else
-            {
-                activity.GenerateW3CContext();
-            }
 
             string[] traceStateValues = HttpHeadersUtilities.SafeGetCommaSeparatedHeaderValues(requestHeaders, W3C.W3CConstants.TraceStateHeader,
                 InjectionGuardConstants.TraceStateHeaderMaxLength, InjectionGuardConstants.TraceStateMaxPairs);
diff --git a/test/Microsoft.ApplicationInsights.AspNetCore.Tests/HostingDiagnosticListenerTest.cs b/test/Microsoft.ApplicationInsights.AspNetCore.Tests/HostingDiagnosticListenerTest.cs
index 87ccc82f..bec25163 100644
--- a/test/Microsoft.ApplicationInsights.AspNetCore.Tests/HostingDiagnosticListenerTest.cs
+++ b/test/Microsoft.ApplicationInsights.AspNetCore.Tests/HostingDiagnosticListenerTest.cs
@@ -836,10 +836,6 @@ public void OnBeginRequestWithW3CSupportAndNoHeadersIsTrackedCorrectly(bool isAs
 
                 var activityInitializedByW3CHeader = Activity.Current;
 
-                if (!isAspNetCore2)
-                { 
-                Assert.Null(activityInitializedByW3CHeader.ParentId);
-                    }
                 Assert.NotNull(activityInitializedByW3CHeader.GetTraceId());
                 Assert.Equal(32, activityInitializedByW3CHeader.GetTraceId().Length);
                 Assert.Equal(16, activityInitializedByW3CHeader.GetSpanId().Length);

From 293c29a43f6d06080e6f488c4f95211af71ad222 Mon Sep 17 00:00:00 2001
From: Dmitry-Matveev <d.g.matveev@gmail.com>
Date: Thu, 11 Apr 2019 14:25:55 -0700
Subject: [PATCH 11/12] Keep Public vs. Internal

---
 .../DiagnosticListeners/Implementation/HeadersUtilities.cs      | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HeadersUtilities.cs b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HeadersUtilities.cs
index 2794f9d4..d99c3233 100644
--- a/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HeadersUtilities.cs
+++ b/src/Microsoft.ApplicationInsights.AspNetCore/DiagnosticListeners/Implementation/HeadersUtilities.cs
@@ -47,7 +47,7 @@ public static string GetHeaderKeyValue(IEnumerable<string> headerValues, string
         /// <param name="keyName">The name of the key to add.</param>
         /// <param name="keyValue">The value of the key to add.</param>
         /// <returns>The result of setting the provided key name/value pair into the provided headerValues.</returns>
-        internal static StringValues SetHeaderKeyValue(string[] currentHeaders, string key, string value)
+        public static StringValues SetHeaderKeyValue(string[] currentHeaders, string key, string value)
         {
             if (currentHeaders != null)
             {

From ff059fd70b72fe91f499a4ae632e600d2160a929 Mon Sep 17 00:00:00 2001
From: Dmitry-Matveev <d.g.matveev@gmail.com>
Date: Thu, 11 Apr 2019 14:40:21 -0700
Subject: [PATCH 12/12] Changelog update

---
 CHANGELOG.md | 1 +
 1 file changed, 1 insertion(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 866a2a67..ca68c918 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 - [Enables Microsoft.Extensions.Logging.ApplicationInsights.ApplicationInsightsLoggerProvider by default. If ApplicationInsightsLoggerProvider was enabled previously using ILoggerFactory extension method, please remove it to prevent duplicate logs.](https://github.com/Microsoft/ApplicationInsights-aspnetcore/issues/854)
 - [Remove reference to Microsoft.Extensions.DiagnosticAdapter and use DiagnosticSource subscription APIs directly](https://github.com/Microsoft/ApplicationInsights-aspnetcore/pull/852) 
 - [Fix: NullReferenceException in ApplicationInsightsLogger.Log when exception contains a Data entry with a null value](https://github.com/Microsoft/ApplicationInsights-aspnetcore/issues/848)
+- [Performance fixes for GetUri, SetKeyHeaderValue, ConcurrentDictionary use and Telemetry Initializers](https://github.com/Microsoft/ApplicationInsights-aspnetcore/pull/864)
 
 ## Version 2.7.0-beta2
 - Added NetStandard2.0 target.