欢迎/初始消息发送两次

Question

我有以下代码，只要用户连接到bot，就会发送消息：

else if (message.Type == ActivityTypes.ConversationUpdate)
        {
            // Handle conversation state changes, like members being added and removed
            // Use Activity.MembersAdded and Activity.MembersRemoved and Activity.Action for info
            // Not available in all channels

            IConversationUpdateActivity update = message;
            var client = new ConnectorClient(new Uri(message.ServiceUrl), new MicrosoftAppCredentials());
            if (update.MembersAdded != null && update.MembersAdded.Any())
            {
                foreach (var newMember in update.MembersAdded)
                {
                    if (newMember.Id != message.Recipient.Id)
                    {
                        var reply = message.CreateReply("Welcome to the ChatBot! Say a 'Hello'");
                        client.Conversations.ReplyToActivity(reply);
                    }
                }
            }
        }

此代码在模拟器上正常工作。但是当谈到Skype和Facebook时，消息会显示两次。 我做错了什么？