From fffe325d44711bbfae849c7812b967cad124bb8c Mon Sep 17 00:00:00 2001
From: sta <sta.blockhead@gmail.com>
Date: Wed, 18 Dec 2019 22:06:48 +0900
Subject: [PATCH] [Modify] Throw an exception

---
 websocket-sharp/Net/HttpListenerResponse.cs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/websocket-sharp/Net/HttpListenerResponse.cs b/websocket-sharp/Net/HttpListenerResponse.cs
index ab40ad6d..062c1ce4 100644
--- a/websocket-sharp/Net/HttpListenerResponse.cs
+++ b/websocket-sharp/Net/HttpListenerResponse.cs
@@ -342,6 +342,11 @@ namespace WebSocketSharp.Net
         if (_disposed)
           throw new ObjectDisposedException (GetType ().ToString ());
 
+        if (_headersSent) {
+          var msg = "The response is already being sent.";
+          throw new InvalidOperationException (msg);
+        }
+
         if (value == null) {
           _contentType = null;
           return;