enable stateful reconnection in bidirection chat sample.

samples/BidirectionChat/csharp/content/index.html

@@ -92,7 +92,7 @@
     </div>
 
     <script src="https://cdn.jsdelivr.net/npm/vue@2.5.17/dist/vue.min.js"></script>
-    <script src="https://cdn.jsdelivr.net/npm/@aspnet/signalr@1.0.3/dist/browser/signalr.js"></script>
+    <script src="https://cdnjs.cloudflare.com/ajax/libs/microsoft-signalr/8.0.0/signalr.js"></script>
     <script src="https://cdn.jsdelivr.net/npm/axios@0.18.0/dist/axios.min.js"></script>
     <script src="https://cdn.jsdelivr.net/npm/crypto-js@3.1.9-1/crypto-js.js"></script>
     <script src="https://cdn.jsdelivr.net/npm/crypto-js@3.1.9-1/enc-base64.js"></script>
@@ -164,6 +164,7 @@
             return generateAccessToken(data.username)
           }
         })
+        .withStatefulReconnect()
         .configureLogging(signalR.LogLevel.Information)
         .build();
       connection.on('newMessage', onNewMessage);