From fc5a7dea8d215fc7ca06e893644c1e6ef922cfac Mon Sep 17 00:00:00 2001
From: sta <sta.blockhead@gmail.com>
Date: Fri, 29 May 2020 19:18:36 +0900
Subject: [PATCH] [Modify] Add it

---
 websocket-sharp/Net/WebHeaderCollection.cs | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/websocket-sharp/Net/WebHeaderCollection.cs b/websocket-sharp/Net/WebHeaderCollection.cs
index 76c55eb3..1e49911f 100644
--- a/websocket-sharp/Net/WebHeaderCollection.cs
+++ b/websocket-sharp/Net/WebHeaderCollection.cs
@@ -798,6 +798,21 @@ namespace WebSocketSharp.Net
       }
     }
 
+    private void checkAllowed (HttpHeaderType headerType)
+    {
+      if (_state == HttpHeaderType.Unspecified)
+        return;
+
+      if (headerType == HttpHeaderType.Unspecified)
+        return;
+
+      if (headerType != _state) {
+        var msg = "This instance does not allow the header.";
+
+        throw new InvalidOperationException (msg);
+      }
+    }
+
     private void checkAllowed (string name)
     {
       if (_state == HttpHeaderType.Unspecified)