Anthem.net 前台调用后台方法探索一

本文主要逐步介绍Anthem.net后台是如何处理的。由于篇幅有限，在本文中所贴出的方法均只列出重点地方，如需一窥全貌请各位读者自行到原码中查找。

1、我们知道需要使用前台Javascript中可以调用后台方法必须加Page_Load中注册本页

        protected void Page_Load(object sender, EventArgs e)
        {
            Anthem.Manager.Register(this);
        }

2、实际上Anthem.Manager.Register(this)，通过调用Manager:AddManager(Page) 方法进行事件绑定。

        private static void AddManager(Page page)
        {
            Manager manager = HttpContext.Current.Items[GetAnthemManagerKey()] as Manager;
            if (manager == null)
            {
                manager = new Manager();
                page.PreRender += new EventHandler(manager.OnPreRender);
                page.Error += new EventHandler(manager.OnError);
                page.Unload += new EventHandler(manager.OnUnload);
                manager._targets[GetAnthemManagerKey()] = manager;
                HttpContext.Current.Items[GetAnthemManagerKey()] = manager;
            }
            manager.RegisterPageScript(page);
        }

3、这样在页面呈现时就会调用Manager:OnPreRender方法，而OnPreRender方法中通过改变HttpRespnose.Filter的输出。

        private void OnPreRender(object source, EventArgs e)
        {
        //省略
                if (invokeMethod)
                {
                    if (targetObject == null)
                    {
                        error = "CONTROLNOTFOUND";
                    }
                    else
                    {
            
                        if (methodName != null && methodName.Length > 0)
                        {
                            MethodInfo methodInfo = FindTargetMethod(targetObject, methodName);
                            if (methodInfo == null)
                            {
                                error = "METHODNOTFOUND";
                            }
                            else
                            {
                                try
                                {
                                    object[] parameters = ConvertParameters(methodInfo, req);
                                    //使用反射调用目标方法
                                    val = InvokeMethod(targetObject, methodInfo, parameters);
                                }
                                catch (MethodAccessException ex)
                                {
                                    if (!methodInfo.IsPublic)
                                        error = string.Format("Anthem.Manager does not have permission to invoke method \"{0}\" in the current trust level. Please try making the method Public.", methodName);
                                    else
                                        error = ex.Message;
                                }
                                catch (Exception ex)
                                {
                                    error = ex.Message;
                                }
                            }
                        }
                    }
                }

                ConfigureResponse(resp);
                //改变当前Response流出的的内容
                resp.Filter = new CallBackFilter(this, resp.Filter);
                _value = val;
                _error = error;
                _updatePage = string.Compare(req["Anthem_UpdatePage"], "true", true) == 0;
                _updateValidationScripts = false;

        //省略

            }
        }

4、CallBackFilter为一个继承Stream的类，主要调用Anthem.Manager.WriteResult方法来获取输出内容

internal class CallBackFilter : Stream
    {
        private Anthem.Manager _manager;
        private Stream _next;
        private MemoryStream _buffer;

        //让_next持有当前输出流的引用,然后改变_next的内容输出
        internal CallBackFilter(Anthem.Manager manager, Stream next)
        {
            _manager = manager;
            _next = next;
            _buffer = new MemoryStream();
        }

        public override void Close()
        {
           //改变输出内容
            _manager.WriteResult(_next, _buffer);
            base.Close();
        }




    }

internal void WriteResult(Stream stream, MemoryStream htmlBuffer)
{
            StringBuilder sb = new StringBuilder();
            try
            {
                WriteValueAndError(sb, _value, _error, viewState, viewStateEncrypted, eventValidation, controls, scripts);
            }
            catch (Exception ex)
            {
                // If an exception was thrown while formatting the
                // result value, we need to discard whatever was
                // written and start over with nothing but the error
                // message.
                sb.Length = 0;
                //写入输出数据
                WriteValueAndError(sb, null, ex.Message, null, null, null, null, null);
            }

            // If an IOFrame was used to make this callback, then wrap the response in a <textarea> element
            // so the iframe will not mess with the text of the JSON object.
            string response = sb.ToString();
            if (string.Compare(HttpContext.Current.Request["Anthem_IOFrame"], "true", true) == 0)
            {
                // If the response text contains any </textarea> tags they will truncate the response
                // on the client. To avoid this, </textarea> tags are converted to </anthemarea> tags
                // here and converted back to </textarea> on the client.
                response = "<textarea id=\"response\">" + Regex.Replace(response, "</textarea>", "</anthemarea>", RegexOptions.IgnoreCase) + "</textarea>";
            }

            byte[] buffer = HttpContext.Current.Response.ContentEncoding.GetBytes(response);
            stream.Write(buffer, 0, buffer.Length);
}

由于本人技术有限，如有错误之处，请各位多指教！