AJaxFileUpload 文件上传<pre>,json字符串为空解决方法

View页面 的JS代码 其中返回值要进行序列号 dataType要大写

    <script type="text/javascript">
       function ajaxFileUpload(){
                $.ajaxFileUpload({
                    url: '/FileUpload/Index', //用于文件上传的服务器端请求地址
                    secureuri: false, //是否需要安全协议，一般设置为false
                    fileElementId: 'fileName', //文件上传域的ID
                    dataType: 'JSON', //返回值类型 一般设置为JSON
                    success: function (data, status)  //服务器成功响应处理函数
                    {
                       var datas = $.parseJSON(data)//此处一定要序列化
                       $("#img_url").val(datas.img_url);
                        
                    },
                    error: function (data)//服务器响应失败处理函数
                    {
                        alert(data.img_url);
                    }
                }
            )
                return false;
}
    </script>

 ajaxFileUpload代码

jQuery.extend({
    createUploadIframe: function (id, uri) {
        //创建 frame
        var frameId = 'jUploadFrame' + id;
        var iframeHtml = '<iframe id="' + frameId + '" name="' + frameId + '" style="position:absolute; top:-9999px; left:-9999px"';
        if (window.ActiveXObject) {
            if (typeof uri == 'boolean') {
                iframeHtml += ' src="' + 'javascript:false' + '"';
            }
            else if (typeof uri == 'string') {
                iframeHtml += ' src="' + uri + '"';
            }
        }
        iframeHtml += ' />';
        jQuery(iframeHtml).appendTo(document.body);
        return jQuery('#' + frameId).get(0);
    },
    createUploadForm: function (id, fileElementId, data) {
        //创建 frame    
        var formId = 'jUploadForm' + id;
        var fileId = 'jUploadFile' + id;
        var form = jQuery('<form  action="" method="POST" name="' + formId + '" id="' + formId + '" enctype="multipart/form-data"></form>');
        if (data) {
            for (var i in data) {
                jQuery('<input type="hidden" name="' + i + '" value="' + data[i] + '" />').appendTo(form);
            }
        }
        var oldElement = jQuery('#' + fileElementId);
        var newElement = jQuery(oldElement).clone();
        jQuery(oldElement).attr('id', fileId);
        jQuery(oldElement).before(newElement);
        jQuery(oldElement).appendTo(form);

        //设置属性
        jQuery(form).css('position', 'absolute');
        jQuery(form).css('top', '-1200px');
        jQuery(form).css('left', '-1200px');
        jQuery(form).appendTo('body');
        return form;
    },

    ajaxFileUpload: function (s) {
        s = jQuery.extend({}, jQuery.ajaxSettings, s);
        var id = new Date().getTime()
        var form = jQuery.createUploadForm(id, s.fileElementId, (typeof (s.data) == 'undefined' ? false : s.data));
        var io = jQuery.createUploadIframe(id, s.secureuri);
        var frameId = 'jUploadFrame' + id;
        var formId = 'jUploadForm' + id;
        // 监控请求
        if (s.global && !jQuery.active++) {
            jQuery.event.trigger("ajaxStart");
        }
        var requestDone = false;
        // 创建请求对象
        var xml = {}
        if (s.global)
            jQuery.event.trigger("ajaxSend", [xml, s]);
        //等待一个响应返回
        var uploadCallback = function (isTimeout) {
            var io = document.getElementById(frameId);
            try {
                if (io.contentWindow) {
                    xml.responseText = io.contentWindow.document.body ? io.contentWindow.document.body.innerHTML : null;
                    xml.responseXML = io.contentWindow.document.XMLDocument ? io.contentWindow.document.XMLDocument : io.contentWindow.document;

                } else if (io.contentDocument) {
                    xml.responseText = io.contentDocument.document.body ? io.contentDocument.document.body.innerHTML : null;
                    xml.responseXML = io.contentDocument.document.XMLDocument ? io.contentDocument.document.XMLDocument : io.contentDocument.document;
                }
            } catch (e) {
                jQuery.handleError(s, xml, null, e);
            }
            if (xml || isTimeout == "timeout") {
                requestDone = true;
                var status;
                try {
                    status = isTimeout != "timeout" ? "success" : "error";
                    //请求成功
                    if (status != "error") {
                        // 处理数据
                        var data = jQuery.uploadHttpData(xml, s.dataType);
                        if (s.success)
                            s.success(data, status);
                        // 触发全局返回
                        if (s.global)
                            jQuery.event.trigger("ajaxSuccess", [xml, s]);
                    } else
                        jQuery.handleError(s, xml, status);
                } catch (e) {
                    status = "error";
                    jQuery.handleError(s, xml, status, e);
                }

                // 请求完成
                if (s.global)
                    jQuery.event.trigger("ajaxComplete", [xml, s]);

                // 处理全局AJAX计数器
                if (s.global && ! --jQuery.active)
                    jQuery.event.trigger("ajaxStop");

                // 处理结果
                if (s.complete)
                    s.complete(xml, status);

                jQuery(io).unbind()

                setTimeout(function () {
                    try {
                        jQuery(io).remove();
                        jQuery(form).remove();

                    } catch (e) {
                        jQuery.handleError(s, xml, null, e);
                    }

                }, 100)

                xml = null

            }
        }
        // 超时检查
        if (s.timeout > 0) {
            setTimeout(function () {
                if (!requestDone) uploadCallback("timeout");
            }, s.timeout);
        }
        try {

            var form = jQuery('#' + formId);
            jQuery(form).attr('action', s.url);
            jQuery(form).attr('method', 'POST');
            jQuery(form).attr('target', frameId);
            if (form.encoding) {
                jQuery(form).attr('encoding', 'multipart/form-data');
            }
            else {
                jQuery(form).attr('enctype', 'multipart/form-data');
            }
            jQuery(form).submit();

        } catch (e) {
            jQuery.handleError(s, xml, null, e);
        }

        jQuery('#' + frameId).load(uploadCallback);
        return { abort: function () { } };

    },

    uploadHttpData: function (r, type) {
        var data = !type;
        data = type == "xml" || data ? r.responseXML : r.responseText;
        if (type == "script")
            jQuery.globalEval(data);
        if (type == "json") {
            data = r.responseText;
            var start = data.indexOf(">");
            if (start != -1) {
                var end = data.indexOf("<", start + 1);
                if (end != -1) {
                    data = data.substring(start + 1, end);
                }
            }
            eval("data = " + data);
            //data = jQuery.parseJSON(jQuery(data).text());
        }
        if (type == "html")
            jQuery("<div>").html(data).evalScripts();
        return data;
    },
    handleError: function (s, xhr, status, e) {
        // If a local callback was specified, fire it
        if (s.error) {
            s.error.call(s.context || s, xhr, status, e);
        }

        // Fire the global callback
        if (s.global) {
            (s.context ? jQuery(s.context) : jQuery.event).trigger("ajaxError", [xhr, s, e]);
        }
    }

})

 后台Controller代码

    public class FileUploadController : Controller
    {
        //
        // GET: /FileUpload/
        [HttpPost]
        public JsonResult Index()
        {
            StringBuilder info = new StringBuilder();
            foreach (string file in Request.Files)
            {
                HttpPostedFileBase postFile = Request.Files[file];//get post file   
                if (postFile.ContentLength == 0)
                {
                    continue;
                }
                string name = DateTime.Now.ToFileTime().ToString();
                string fileExrensio = System.IO.Path.GetExtension(Request.Files[file].FileName).ToLower();
                string newFilePath = System.Web.HttpContext.Current.Server.MapPath("/upload/");//save path   
                postFile.SaveAs(newFilePath + name + fileExrensio);//save file   
                info.Append("/upload/" + name + fileExrensio);
            }
            return Json(new { img_url = info.ToString() }, "text/html;charset=UTF-8");//一定要制定格式
        }

    }