微信公众平台开发学习系列（二）：微信公众平台接收消息与发送消息

本篇主要介绍如何使用senparc来处理微信公众平台的接收消息与发送消息。

首先微信端会将用户的发送的信息以post请求发送到填写的url上，服务端代码如下：

        [HttpPost]
        public ActionResult Get(PostModel postModel)
        {
            var messageHandler = new CustomMessageHandler(Request.InputStream, postModel);

            messageHandler.Execute();//执行微信处理过程

            return Content(messageHandler.ResponseDocument.ToString());
        }

新建一个CustomMessageHandler类和一个CustomMessageContext类，CustomMessageHandler类继承MessageHandler<CustomMessageContext>，CustomMessageContext类继承MessageContext<IRequestMessageBase,IResponseMessageBase>，CustomMessageContext类的方法此处不贴出，主要是实现CustomMessageHandler类的方法，代码如下：

        public CustomMessageHandler(Stream inputStream, PostModel postModel)
            : base(inputStream, postModel)
        {

        }

        public override IResponseMessageBase DefaultResponseMessage(IRequestMessageBase requestMessage)
        {
            var responseMessage = base.CreateResponseMessage<ResponseMessageText>(); //ResponseMessageText指返回文本信息
            responseMessage.Content = "这条消息来自DefaultResponseMessage。"+requestMessage.MsgId;
            return responseMessage;
        }

返回信息的格式多种多样，如：ResponseMessageText，ResponseMessageNews，ResponseMessageImage等。接收信息的格式也分很多种，不同格式有不同的处理方法：OnTextRequest，OnImageRequest,OnEvent_ViewRequest等。如果没有重写相应方法，就默认执行DefaultResponseMessage方法。本篇重写2个方法作为简单的例子。

用户发送文本信息情况下的返回信息处理

        public override IResponseMessageBase OnTextRequest(RequestMessageText requestMessage)
        {
            var responseMessage = base.CreateResponseMessage<ResponseMessageText>();
            responseMessage.Content = "您的OpenID是：" + requestMessage.FromUserName     
                                    + "。
您发送了文字信息：" + requestMessage.Content; 
            return responseMessage;
        }

菜单点击事件情况下的返回信息处理

        public override IResponseMessageBase OnEvent_ClickRequest(RequestMessageEvent_Click requestMessage)
        {
            IResponseMessageBase reponseMessage = null;
            //菜单点击，需要跟创建菜单时的Key匹配
            switch (requestMessage.EventKey)
            {
                case "OneClick":
                    {
                        var strongResponseMessage = CreateResponseMessage<ResponseMessageNews>();
                        reponseMessage = strongResponseMessage;
                        strongResponseMessage.Articles.Add(new Article()
                        {
                            Title = "您点击了菜单图文按钮",
                            Description = "您点击图文链接按钮，这是一条图文信息。",
                            PicUrl = "https://ss2.baidu.com/6ONYsjip0QIZ8tyhnq/it/u=3233073314,694013259&fm=58&s=39C718720E8EBE011B398BAC0300F024",
                            Url = "http://www.baidu.com"
                        });
                    }
                    break;
                case "SubClickRoot_Text":
                    {
                        var strongResponseMessage = CreateResponseMessage<ResponseMessageText>();
                        reponseMessage = strongResponseMessage;
                        strongResponseMessage.Content = "您点击了子菜单按钮。";
                    }
                    break;
                default:
                    {
                        var strongResponseMessage = CreateResponseMessage<ResponseMessageText>();
                        strongResponseMessage.Content = "您点击了按钮，EventKey：" + requestMessage.EventKey;
                        reponseMessage = strongResponseMessage;
                    }
                    break;
            }

            return reponseMessage;
        }