实体框架数据访问尝试时，WCF Websocket项目失败

Question

我是WebSockets的新手（这个AM）并设置了一个WCF WebSocket应用程序，当我在网上找到一个简单的例子时可以正常工作（http://www.codeproject.com/Articles/619343/Using-WebSocket-in-NET-Part）。

我添加了实体框架，只要我添加代码以尝试访问数据，该过程（只是来回发送消息）就不再有效了。

我可能会遗漏一些基本概念吗？

有没有人对故障排除有任何好的想法？

namespace PBWebSocket
{
    public class PBWebSocket : IBWebSocket
    {

        private SPEntities db = new SPEntities();

        public async Task SendMessageToServer(Message msg)
        {
            var callback = OperationContext.Current.GetCallbackChannel<IPBCallback>();
            if (msg.IsEmpty || ((IChannel)callback).State != CommunicationState.Opened)
            {
                return;
            }

            byte[] body = msg.GetBody<byte[]>();
            string msgTextFromClient = Encoding.UTF8.GetString(body);
            var reqId = Int32.Parse(msgTextFromClient);

            // *** The below line breaks it ***
            var req = db.Requests.Where(r => r.Id == 164).FirstOrDefault();

            reqId = reqId + 2;
            Message newMsg = ByteStreamMessage.CreateMessage(
            new ArraySegment<byte>(Encoding.UTF8.GetBytes(reqId.ToString())));
              newMsg.Properties["WebSocketMessageProperty"] =
            new WebSocketMessageProperty
              { MessageType = WebSocketMessageType.Text };

            await callback.SendMessageToClient(newMsg);
        }
    }
}