ASP.NET 中使用 ICallbackEventHanlder做 ajax 请求参数长度限制问题

本帖最后由 willwayer23 于 2011-03-17 08:56:37 编辑

解决方案 »

  1.   

    解决了  GetCallbackEventReference 底层实现
       //用于存放所有未完成的callback对象的数组__pendingCallbacks
    var __pendingCallbacks = new Array();
    var __synchronousCallBackIndex = -1;//回调主函数WebForm_DoCallback
    function WebForm_DoCallback(eventTarget, eventArgument, eventCallback, context, errorCallback, useAsync) {    //构造回调参数，回调参数包括了原来页面上的formpostdata和我们传递的目标控件、eventArgument和部分验证信息
        var postData = __theFormPostData +
                    "__CALLBACKID=" + WebForm_EncodeCallback(eventTarget) +
                    "&__CALLBACKPARAM=" + WebForm_EncodeCallback(eventArgument);
        if (theForm["__EVENTVALIDATION"]) {
            postData += "&__EVENTVALIDATION=" + WebForm_EncodeCallback(theForm["__EVENTVALIDATION"].value);
        }
       
       //下面实例化XMLHTTP对象，如果浏览器支持XMLHTTP则直接用XMLHTTP执行异步回调
        var xmlRequest,e;
        try {
            xmlRequest = new XMLHttpRequest();
        }
        catch(e) {
            try {
                xmlRequest = new ActiveXObject("Microsoft.XMLHTTP");
            }
            catch(e) {
            }
        }
        var setRequestHeaderMethodExists = true;
        try {
            setRequestHeaderMethodExists = (xmlRequest && xmlRequest.setRequestHeader);
        }
        catch(e) {}
        var callback = new Object();
        callback.eventCallback = eventCallback;
        callback.context = context;
        callback.errorCallback = errorCallback;
        callback.async = useAsync;
        
       //获取对应的回调对象 
        var callbackIndex = WebForm_FillFirstAvailableSlot(__pendingCallbacks, callback);
        if (!useAsync) {
            if (__synchronousCallBackIndex != -1) {
                __pendingCallbacks[__synchronousCallBackIndex] = null;
            }
            __synchronousCallBackIndex = callbackIndex;
        }
        if (setRequestHeaderMethodExists) {
            xmlRequest.onreadystatechange = WebForm_CallbackComplete;
            callback.xmlRequest = xmlRequest;
            xmlRequest.open("POST", theForm.action, true);
            xmlRequest.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
            xmlRequest.send(postData);
            return;
        }
       
       //万一浏览器不支持XMLHTTP的话，我们IFRAME方案代替，在一个隐藏的IFRAME中执行Postback   
        callback.xmlRequest = new Object();
        var callbackFrameID = "__CALLBACKFRAME" + callbackIndex;
        var xmlRequestFrame = document.frames[callbackFrameID];
        if (!xmlRequestFrame) {
            xmlRequestFrame = document.createElement("IFRAME");
            xmlRequestFrame.width = "1";
            xmlRequestFrame.height = "1";
            xmlRequestFrame.frameBorder = "0";
            xmlRequestFrame.id = callbackFrameID;
            xmlRequestFrame.name = callbackFrameID;
            xmlRequestFrame.style.position = "absolute";
            xmlRequestFrame.style.top = "-100px"
            xmlRequestFrame.style.left = "-100px";
            try {
                if (callBackFrameUrl) {
                    xmlRequestFrame.src = callBackFrameUrl;
                }
            }
            catch(e) {}
            document.body.appendChild(xmlRequestFrame);
        }
        var interval = window.setInterval(function() {
            xmlRequestFrame = document.frames[callbackFrameID];
            if (xmlRequestFrame && xmlRequestFrame.document) {
                window.clearInterval(interval);
                xmlRequestFrame.document.write("");
                xmlRequestFrame.document.close();
                xmlRequestFrame.document.write('<html><body><form method="post"><input type="hidden" name="__CALLBACKLOADSCRIPT" value="t"></form></body></html>');
                xmlRequestFrame.document.close();
                xmlRequestFrame.document.forms[0].action = theForm.action;
                var count = __theFormPostCollection.length;
                var element;
                for (var i = 0; i < count; i++) {
                    element = __theFormPostCollection[i];
                    if (element) {
                        var fieldElement = xmlRequestFrame.document.createElement("INPUT");
                        fieldElement.type = "hidden";
                        fieldElement.name = element.name;
                        fieldElement.value = element.value;
                        xmlRequestFrame.document.forms[0].appendChild(fieldElement);
                    }
                }
                var callbackIdFieldElement = xmlRequestFrame.document.createElement("INPUT");
                callbackIdFieldElement.type = "hidden";
                callbackIdFieldElement.name = "__CALLBACKID";
                callbackIdFieldElement.value = eventTarget;
                xmlRequestFrame.document.forms[0].appendChild(callbackIdFieldElement);
                var callbackParamFieldElement = xmlRequestFrame.document.createElement("INPUT");
                callbackParamFieldElement.type = "hidden";
                callbackParamFieldElement.name = "__CALLBACKPARAM";
                callbackParamFieldElement.value = eventArgument;
                xmlRequestFrame.document.forms[0].appendChild(callbackParamFieldElement);
                if (theForm["__EVENTVALIDATION"]) {
                    var callbackValidationFieldElement = xmlRequestFrame.document.createElement("INPUT");
                    callbackValidationFieldElement.type = "hidden";
                    callbackValidationFieldElement.name = "__EVENTVALIDATION";
                    callbackValidationFieldElement.value = theForm["__EVENTVALIDATION"].value;
                    xmlRequestFrame.document.forms[0].appendChild(callbackValidationFieldElement);
                }
                var callbackIndexFieldElement = xmlRequestFrame.document.createElement("INPUT");
                callbackIndexFieldElement.type = "hidden";
                callbackIndexFieldElement.name = "__CALLBACKINDEX";
                callbackIndexFieldElement.value = callbackIndex;
                xmlRequestFrame.document.forms[0].appendChild(callbackIndexFieldElement);
                xmlRequestFrame.document.forms[0].submit();
            }
        }, 10);
    }//该函数在每次回调结束后会调用来检查当前的回调列表中的回调的执行情况，如果，执行完毕的，则从列表中删除回调对象，并删除临时建立的IFRAME
    function WebForm_CallbackComplete() {
        for (i = 0; i < __pendingCallbacks.length; i++) {
            callbackObject = __pendingCallbacks[i];
            if (callbackObject && callbackObject.xmlRequest && (callbackObject.xmlRequest.readyState == 4)) {
                WebForm_ExecuteCallback(callbackObject);
                if (!__pendingCallbacks[i].async) {
                    __synchronousCallBackIndex = -1;
                }
                __pendingCallbacks[i] = null;
                var callbackFrameID = "__CALLBACKFRAME" + i;
                var xmlRequestFrame = document.getElementById(callbackFrameID);
                if (xmlRequestFrame) {
                    xmlRequestFrame.parentNode.removeChild(xmlRequestFrame);
                }
            }
        }
    }//该函数执行我们在回调激发端指定的处理返回数据的script函数，如我们上面范例代码中的ReceiveServerData函数
    function WebForm_ExecuteCallback(callbackObject) {
        var response = callbackObject.xmlRequest.responseText;
        if (response.charAt(0) == "s") {
            if ((typeof(callbackObject.eventCallback) != "undefined") && (callbackObject.eventCallback != null)) {
                callbackObject.eventCallback(response.substring(1), callbackObject.context);
            }
        }
        else if (response.charAt(0) == "e") {
            if ((typeof(callbackObject.errorCallback) != "undefined") && (callbackObject.errorCallback != null)) {
                callbackObject.errorCallback(response.substring(1), callbackObject.context);
            }
        }
        else {
            var separatorIndex = response.indexOf("|");
            if (separatorIndex != -1) {
                var validationFieldLength = parseInt(response.substring(0, separatorIndex));
                if (!isNaN(validationFieldLength)) {
                    var validationField = response.substring(separatorIndex + 1, separatorIndex + validationFieldLength + 1);
                    if (validationField != "") {
                        var validationFieldElement = theForm["__EVENTVALIDATION"];
                        if (!validationFieldElement) {
                            validationFieldElement = document.createElement("INPUT");
                            validationFieldElement.type = "hidden";
                            validationFieldElement.name = "__EVENTVALIDATION";
                            theForm.appendChild(validationFieldElement);
                        }
                        validationFieldElement.value = validationField;
                    }
                    if ((typeof(callbackObject.eventCallback) != "undefined") && (callbackObject.eventCallback != null)) {
                        callbackObject.eventCallback(response.substring(separatorIndex + validationFieldLength + 1), callbackObject.context);
                    }
                }
            }
        }
    }//获取对应的回调对象 
    function WebForm_FillFirstAvailableSlot(array, element) {
        var i;
        for (i = 0; i < array.length; i++) {
            if (!array[i]) break;
        }
        array[i] = element;
        return i;
    }
      

  2.   


    //POST方式
    xmlRequest.open("POST", theForm.action, true);
      

  3.   

    除了查看源码， httpwatch、Fiddler 等监测工具也可以知道