From a7c9e8ab25b7fbadb2153a2f0a81e717c9c52bd9 Mon Sep 17 00:00:00 2001
From: "Chris Ross (ASP.NET)" <chrross@microsoft.com>
Date: Thu, 9 Nov 2017 08:57:20 -0800
Subject: [PATCH] Test: Do not set response headers after the response has
 started

---
 .../FiltersWebSite/Filters/TracingResourceFilter.cs      | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/test/WebSites/FiltersWebSite/Filters/TracingResourceFilter.cs b/test/WebSites/FiltersWebSite/Filters/TracingResourceFilter.cs
index 264daa1bfc..275a3a32ba 100644
--- a/test/WebSites/FiltersWebSite/Filters/TracingResourceFilter.cs
+++ b/test/WebSites/FiltersWebSite/Filters/TracingResourceFilter.cs
@@ -18,9 +18,12 @@ namespace FiltersWebSite
 
         public void OnResourceExecuted(ResourceExecutedContext context)
         {
-            context.HttpContext.Response.Headers.Append(
-                "filters", 
-                Name + " - OnResourceExecuted");
+            if (!context.HttpContext.Response.HasStarted)
+            {
+                context.HttpContext.Response.Headers.Append(
+                    "filters",
+                    Name + " - OnResourceExecuted");
+            }
         }
 
         public void OnResourceExecuting(ResourceExecutingContext context)