Added ${aspnet-response-statuscode} - rendering response status code

src/Shared/Internal/HttpContextExtensions.cs

@@ -28,6 +28,22 @@ internal static HttpRequestBase TryGetRequest(this HttpContextBase context)
                 return null;
             }
         }
+
+        internal static HttpResponseBase TryGetResponse(this HttpContextBase context)
+        {
+            try
+            {
+                var response = context?.Response;
+                if (response == null)
+                    InternalLogger.Debug("HttpContext Response Lookup returned null");
+                return response;
+            }
+            catch (HttpException ex)
+            {
+                InternalLogger.Debug(ex, "HttpContext Response Lookup failed.");
+                return null;
+            }
+        }
 #else
         internal static HttpRequest TryGetRequest(this HttpContext context)
         {
@@ -36,6 +52,14 @@ internal static HttpRequest TryGetRequest(this HttpContext context)
                 InternalLogger.Debug("HttpContext Request Lookup returned null");
             return request;
         }
+
+        internal static HttpResponse TryGetResponse(this HttpContext context)
+        {
+            var response = context?.Response;
+            if (response == null)
+                InternalLogger.Debug("HttpContext Response Lookup returned null");
+            return response;
+        }
 #endif
 
 #if ASP_NET_CORE

src/Shared/LayoutRenderers/AspNetResponseStatusCodeRenderer.cs

@@ -0,0 +1,46 @@
+using System.Text;
+using NLog.Config;
+using NLog.LayoutRenderers;
+using NLog.Web.Internal;
+
+namespace NLog.Web.LayoutRenderers
+{
+    /// <summary>
+    /// ASP.NET Response Status Code.
+    /// </summary>
+    /// <para>Example usage of ${aspnet-response-statuscode}:</para>
+    /// <example>
+    /// <code lang="NLog Layout Renderer">
+    /// ${aspnet-response-statuscode} - Produces - 200.
+    /// </code>
+    /// </example>
+    [LayoutRenderer("aspnet-response-statuscode")]
+    [ThreadSafe]
+    public class AspNetResponseStatusCodeRenderer : AspNetLayoutRendererBase
+    {
+        /// <summary>
+        /// ASP.NET Http Response Status Code
+        /// </summary>
+        /// <param name="builder">The <see cref="StringBuilder" /> to append the rendered data to.</param>
+        /// <param name="logEvent">Logging event.</param>
+        protected override void DoAppend(StringBuilder builder, LogEventInfo logEvent)
+        {
+            var httpResponse = HttpContextAccessor.HttpContext.TryGetResponse();
+            if (httpResponse == null)
+            {
+                return;
+            }
+
+            int statusCode;
+#if !ASP_NET_CORE
+            statusCode = httpResponse.StatusCode;
+#else
+            statusCode = httpResponse.StatusCode;
+#endif
+            if (statusCode >= 100 && statusCode <= 599)
+            {
+                builder.Append(statusCode);
+            }
+        }
+    }
+}

tests/Shared/LayoutRenderers/AspNetResponseStatusCodeRendererTests.cs

@@ -0,0 +1,49 @@
+using NLog.Web.LayoutRenderers;
+using NSubstitute;
+using Xunit;
+
+namespace NLog.Web.Tests.LayoutRenderers
+{
+    public class AspNetResponseStatusCodeRendererTests : LayoutRenderersTestBase<AspNetResponseStatusCodeRenderer>
+    {
+        [Fact]
+        public void StatusCode_Set_Renderer()
+        {
+            // Arrange
+            var (renderer, httpContext) = CreateWithHttpContext();
+            httpContext.Response.StatusCode.Returns(200);
+
+            // Act
+            string result = renderer.Render(new LogEventInfo());
+
+            // Assert
+            Assert.Equal("200", result);
+        }
+
+        [Theory]
+        [InlineData(0, false)]
+        [InlineData(99, false)]
+        [InlineData(100, true)]
+        [InlineData(599, true)]
+        [InlineData(600, false)]
+        public void Only_Render_Valid_StatusCodes(int statusCode, bool shouldBeRendered)
+        {
+            // Arrange
+            var (renderer, httpContext) = CreateWithHttpContext();
+            httpContext.Response.StatusCode.Returns(statusCode);
+
+            // Act
+            string result = renderer.Render(new LogEventInfo());
+
+            // Assert
+            if (shouldBeRendered)
+            {
+                Assert.Equal($"{statusCode}", result);
+            }
+            else
+            {
+                Assert.Empty(result);
+            }
+        }
+    }
+}