From 57c8b71b4dae98f969f43a0386c14422fb1f2a07 Mon Sep 17 00:00:00 2001
From: Javier Calvarro Nelson <jacalvar@microsoft.com>
Date: Fri, 29 Dec 2017 18:56:22 -0800
Subject: [PATCH] [Fixes #6547] Re-introduce HttpMethodActionConstraint
 dictionary perf improvement

---
 .../Internal/CorsHttpMethodActionConstraint.cs               | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/Microsoft.AspNetCore.Mvc.Cors/Internal/CorsHttpMethodActionConstraint.cs b/src/Microsoft.AspNetCore.Mvc.Cors/Internal/CorsHttpMethodActionConstraint.cs
index 8b5c6f57cb..71ba2d696c 100644
--- a/src/Microsoft.AspNetCore.Mvc.Cors/Internal/CorsHttpMethodActionConstraint.cs
+++ b/src/Microsoft.AspNetCore.Mvc.Cors/Internal/CorsHttpMethodActionConstraint.cs
@@ -35,8 +35,9 @@ namespace Microsoft.AspNetCore.Mvc.Cors.Internal
             }
 
             var request = context.RouteContext.HttpContext.Request;
-            if (request.Headers.ContainsKey(OriginHeader) &&
-                string.Equals(request.Method, PreflightHttpMethod, StringComparison.OrdinalIgnoreCase) &&
+            // Perf: Check http method before accessing the Headers collection.
+            if (string.Equals(request.Method, PreflightHttpMethod, StringComparison.OrdinalIgnoreCase) &&
+                request.Headers.ContainsKey(OriginHeader) &&
                 request.Headers.TryGetValue(AccessControlRequestMethod, out var accessControlRequestMethod) &&
                 !StringValues.IsNullOrEmpty(accessControlRequestMethod))
             {