From 484cfa7d77c4c821b6c69697f9f3c400aea04156 Mon Sep 17 00:00:00 2001
From: Rolf Kristensen <sweaty1@hotmail.com>
Date: Wed, 28 Dec 2022 14:09:29 +0100
Subject: [PATCH] AspNetLayoutRendererBase - Skip allocating extra
 HttpContextWrapper

---
 src/NLog.Web/DefaultHttpContextAccessor.cs          |  6 +++++-
 src/NLog.Web/IHttpContextAccessor.cs                |  5 +++++
 src/Shared/Internal/HttpContextExtensions.cs        | 13 +++++++++++++
 .../LayoutRenderers/AspNetLayoutRendererBase.cs     | 11 ++---------
 4 files changed, 25 insertions(+), 10 deletions(-)

diff --git a/src/NLog.Web/DefaultHttpContextAccessor.cs b/src/NLog.Web/DefaultHttpContextAccessor.cs
index b37281ec..47625d83 100644
--- a/src/NLog.Web/DefaultHttpContextAccessor.cs
+++ b/src/NLog.Web/DefaultHttpContextAccessor.cs
@@ -5,7 +5,7 @@ namespace NLog.Web
     /// <summary>
     /// Provides the HttpContext associated with the current request.
     /// </summary>
-    public class DefaultHttpContextAccessor : IHttpContextAccessor
+    public class DefaultHttpContextAccessor : IHttpContextAccessor, IHttpContextAccessorValidation
     {
         /// <summary>
         /// HttpContext of the current request.
@@ -21,5 +21,9 @@ public HttpContextBase HttpContext
             }
         }
 
+        bool IHttpContextAccessorValidation.HasActiveHttpContext()
+        {
+            return System.Web.HttpContext.Current != null;  // Skip allocating HttpContextWrapper
+        }
     }
 }
\ No newline at end of file
diff --git a/src/NLog.Web/IHttpContextAccessor.cs b/src/NLog.Web/IHttpContextAccessor.cs
index b55655df..47cc521a 100644
--- a/src/NLog.Web/IHttpContextAccessor.cs
+++ b/src/NLog.Web/IHttpContextAccessor.cs
@@ -14,4 +14,9 @@ public interface IHttpContextAccessor
         /// </summary>
         HttpContextBase HttpContext { get; }
     }
+
+    internal interface IHttpContextAccessorValidation
+    {
+        bool HasActiveHttpContext();
+    }
 }
\ No newline at end of file
diff --git a/src/Shared/Internal/HttpContextExtensions.cs b/src/Shared/Internal/HttpContextExtensions.cs
index 07b566c3..f6801384 100644
--- a/src/Shared/Internal/HttpContextExtensions.cs
+++ b/src/Shared/Internal/HttpContextExtensions.cs
@@ -17,6 +17,14 @@ namespace NLog.Web.Internal
     internal static class HttpContextExtensions
     {
 #if !ASP_NET_CORE
+        internal static bool HasActiveHttpContext(this IHttpContextAccessor httpContextAccessor)
+        {
+            if (httpContextAccessor is IHttpContextAccessorValidation httpContextAccessorValidation)
+                return httpContextAccessorValidation.HasActiveHttpContext();    // Skip allocating HttpContextWrapper
+            else
+                return httpContextAccessor?.HttpContext != null;
+        }
+
         internal static HttpRequestBase TryGetRequest(this HttpContextBase context)
         {
             try
@@ -49,6 +57,11 @@ internal static HttpResponseBase TryGetResponse(this HttpContextBase context)
             }
         }
 #else
+        internal static bool HasActiveHttpContext(this IHttpContextAccessor httpContextAccessor)
+        {
+            return httpContextAccessor?.HttpContext != null;
+        }
+
         internal static WebSocketManager TryGetWebSocket(this HttpContext context)
         {
             var websocket = context?.WebSockets;
diff --git a/src/Shared/LayoutRenderers/AspNetLayoutRendererBase.cs b/src/Shared/LayoutRenderers/AspNetLayoutRendererBase.cs
index a6ad541f..82df01d8 100644
--- a/src/Shared/LayoutRenderers/AspNetLayoutRendererBase.cs
+++ b/src/Shared/LayoutRenderers/AspNetLayoutRendererBase.cs
@@ -1,10 +1,10 @@
 using System;
-using System.Linq;
 using System.Text;
 
 using NLog.Common;
 using NLog.Config;
 using NLog.LayoutRenderers;
+using NLog.Web.Internal;
 #if ASP_NET_CORE
 using Microsoft.AspNetCore.Http;
 using HttpContextBase = Microsoft.AspNetCore.Http.HttpContext;
@@ -40,7 +40,6 @@ public IHttpContextAccessor HttpContextAccessor
         internal static IHttpContextAccessor DefaultHttpContextAccessor { get; set; } = new DefaultHttpContextAccessor();
         internal static IHttpContextAccessor RetrieveHttpContextAccessor(IServiceProvider serviceProvider, LoggingConfiguration loggingConfiguration) => DefaultHttpContextAccessor;
 #else
-
         internal static IHttpContextAccessor RetrieveHttpContextAccessor(IServiceProvider serviceProvider, LoggingConfiguration loggingConfiguration)
         {
             return ServiceLocator.ResolveService<IHttpContextAccessor>(serviceProvider, loggingConfiguration);
@@ -54,13 +53,7 @@ internal static IHttpContextAccessor RetrieveHttpContextAccessor(IServiceProvide
         /// <param name="logEvent">Logging event.</param>
         protected override void Append(StringBuilder builder, LogEventInfo logEvent)
         {
-            var httpContextAccessor = HttpContextAccessor;
-            if (httpContextAccessor == null)
-            {
-                return;
-            }
-
-            if (httpContextAccessor.HttpContext == null)
+            if (!httpContextAccessor.HasActiveHttpContext())
             {
                 InternalLogger.Debug("No available HttpContext, because outside valid request context. Logger: {0}", logEvent.LoggerName);
                 return;