From bd26e899640d65df9133906acb0edef2e881fc43 Mon Sep 17 00:00:00 2001
From: Christian Zuellig <christian.zuellig@mondaycoffee.com>
Date: Fri, 21 May 2021 07:37:00 +0200
Subject: [PATCH] respect that http header keys are most of the times not case
 sensitiv for compare with existing

---
 src/sdk/PnP.Core/Services/Core/BatchClient.cs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/sdk/PnP.Core/Services/Core/BatchClient.cs b/src/sdk/PnP.Core/Services/Core/BatchClient.cs
index ebf80fefcb..77604a2ef7 100644
--- a/src/sdk/PnP.Core/Services/Core/BatchClient.cs
+++ b/src/sdk/PnP.Core/Services/Core/BatchClient.cs
@@ -775,13 +775,14 @@ private Tuple<string, string> BuildMicrosoftGraphBatchRequestContent(Batch batch
                     {
                         foreach(var key in request.ApiCall.Headers.Keys)
                         {
-                            if(!graphRequest.Headers.ContainsKey(key))
+                            string existingKey = graphRequest.Headers.Keys.FirstOrDefault(k => k.Equals(key, StringComparison.InvariantCultureIgnoreCase));
+                            if (string.IsNullOrWhiteSpace(existingKey))
                             {
                                 graphRequest.Headers.Add(key, request.ApiCall.Headers[key]);
                             }
                             else
                             {
-                                graphRequest.Headers[key] = request.ApiCall.Headers[key];
+                                graphRequest.Headers[existingKey] = request.ApiCall.Headers[key];
                             }
                         }
                     }