From 900686c21b9d09023dc853a03608687ad5728e70 Mon Sep 17 00:00:00 2001
From: Julian Verdurmen <304NotModified@users.noreply.github.com>
Date: Sat, 24 Dec 2016 01:57:04 +0100
Subject: [PATCH] added null checks

---
 NLog.Web.AspNetCore/Internal/PropertyReader.cs | 18 +++++++++++++-----
 .../AspNetItemValueLayoutRenderer.cs           |  5 +++++
 .../AspNetRequestValueLayoutRenderer.cs        |  2 +-
 .../AspNetSessionIDLayoutRenderer.cs           |  2 +-
 .../AspNetSessionValueLayoutRenderer.cs        |  2 +-
 5 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/NLog.Web.AspNetCore/Internal/PropertyReader.cs b/NLog.Web.AspNetCore/Internal/PropertyReader.cs
index 4361f3ae..dcd35a67 100644
--- a/NLog.Web.AspNetCore/Internal/PropertyReader.cs
+++ b/NLog.Web.AspNetCore/Internal/PropertyReader.cs
@@ -28,10 +28,18 @@ public static object GetValue(string key, Func<string, object> getVal, bool eval
 
                 value = getVal(path.First());
 
-                foreach (var property in path.Skip(1))
+                if (value != null)
                 {
-                    var propertyInfo = GetPropertyInfo(value, property);
-                    value = propertyInfo?.GetValue(value, null);
+                    foreach (var property in path.Skip(1))
+                    {
+                        var propertyInfo = GetPropertyInfo(value, property);
+                        value = propertyInfo?.GetValue(value, null);
+                        if (value == null)
+                        {
+                            //done
+                            break;
+                        }
+                    }
                 }
             }
             else
@@ -44,9 +52,9 @@ public static object GetValue(string key, Func<string, object> getVal, bool eval
         private static PropertyInfo GetPropertyInfo(object value, string propertyName)
         {
 #if !NETSTANDARD_1plus
-            return value.GetType().GetProperty(propertyName);
+            return value?.GetType().GetProperty(propertyName);
 #else
-            return value.GetType().GetTypeInfo().GetDeclaredProperty(propertyName);
+            return value?.GetType().GetTypeInfo().GetDeclaredProperty(propertyName);
 #endif
         }
     }
diff --git a/NLog.Web.AspNetCore/LayoutRenderers/AspNetItemValueLayoutRenderer.cs b/NLog.Web.AspNetCore/LayoutRenderers/AspNetItemValueLayoutRenderer.cs
index e41cd25c..3eea0e14 100644
--- a/NLog.Web.AspNetCore/LayoutRenderers/AspNetItemValueLayoutRenderer.cs
+++ b/NLog.Web.AspNetCore/LayoutRenderers/AspNetItemValueLayoutRenderer.cs
@@ -68,6 +68,11 @@ protected override void DoAppend(StringBuilder builder, LogEventInfo logEvent)
             }
             var context = HttpContextAccessor.HttpContext;
 
+            if (context == null)
+            {
+                return;
+            }
+
             Func<string, object> getVal = k => context.Items[k];
 
             var value = PropertyReader.GetValue(Variable, getVal, EvaluateAsNestedProperties);
diff --git a/NLog.Web.AspNetCore/LayoutRenderers/AspNetRequestValueLayoutRenderer.cs b/NLog.Web.AspNetCore/LayoutRenderers/AspNetRequestValueLayoutRenderer.cs
index 55eed2c4..2ee886a0 100644
--- a/NLog.Web.AspNetCore/LayoutRenderers/AspNetRequestValueLayoutRenderer.cs
+++ b/NLog.Web.AspNetCore/LayoutRenderers/AspNetRequestValueLayoutRenderer.cs
@@ -83,7 +83,7 @@ public class AspNetRequestValueLayoutRenderer : AspNetLayoutRendererBase
         /// <param name="logEvent">Logging event.</param>
         protected override void DoAppend(StringBuilder builder, LogEventInfo logEvent)
         {
-            var httpRequest = HttpContextAccessor.HttpContext.TryGetRequest();
+            var httpRequest = HttpContextAccessor?.HttpContext?.TryGetRequest();
             if (httpRequest == null)
             {
                 return;
diff --git a/NLog.Web.AspNetCore/LayoutRenderers/AspNetSessionIDLayoutRenderer.cs b/NLog.Web.AspNetCore/LayoutRenderers/AspNetSessionIDLayoutRenderer.cs
index 94dfb3b5..94271e52 100644
--- a/NLog.Web.AspNetCore/LayoutRenderers/AspNetSessionIDLayoutRenderer.cs
+++ b/NLog.Web.AspNetCore/LayoutRenderers/AspNetSessionIDLayoutRenderer.cs
@@ -23,7 +23,7 @@ protected override void DoAppend(StringBuilder builder, LogEventInfo logEvent)
         {
             var context = HttpContextAccessor.HttpContext;
 
-            if (context.Session == null)
+            if (context?.Session == null)
             {
                 return;
             }
diff --git a/NLog.Web.AspNetCore/LayoutRenderers/AspNetSessionValueLayoutRenderer.cs b/NLog.Web.AspNetCore/LayoutRenderers/AspNetSessionValueLayoutRenderer.cs
index 98dd32a2..958eb514 100644
--- a/NLog.Web.AspNetCore/LayoutRenderers/AspNetSessionValueLayoutRenderer.cs
+++ b/NLog.Web.AspNetCore/LayoutRenderers/AspNetSessionValueLayoutRenderer.cs
@@ -71,7 +71,7 @@ protected override void DoAppend(StringBuilder builder, LogEventInfo logEvent)
             }
 
             var context = HttpContextAccessor.HttpContext;
-            if (context.Session == null)
+            if (context?.Session == null)
             {
                 return;
             }