HTML5文件拖拽上传记录

JS文件：
var FileName = "";
var FileStr = "";
(function () {
    function $id(id) {
        return document.getElementById(id);
    }
    function Output(msg) {
        var m = $id("filedrag");
        m.innerHTML = msg + m.innerHTML;
    }
    function FileDragHover(e) {
        e.stopPropagation();
        e.preventDefault();
        e.target.className = (e.type == "dragover" ? "hover" : "");
    }
    function FileSelectHandler(e) {
        FileDragHover(e);
        var files = e.target.files || e.dataTransfer.files;
        for (var i = 0, f; f = files[i]; i++) {
            ParseFile(f);
            UploadFile(f); //暂时注释
        }
    }
    function ParseFile(file) {

        //pic类型
        if (file.type.indexOf("image") == 0) {
            var reader = new FileReader();
            reader.onload = function (e) {
                Output(
                    "<p><strong>" + file.name + ":</strong><br />" +
                    '<img src="' + e.target.result + '" /></p>'
                );
                FileStr=e.target.result;
            }
            reader.readAsDataURL(file);
        }
        //文本类型处理
        if (file.type.indexOf("text") == 0) {
            var reader = new FileReader();
            reader.onload = function (e) {
                Output(
                    "<p><strong>" + file.name + ":</strong></p><pre>" +
                    e.target.result.replace(/</g, "&lt;").replace(/>/g, "&gt;") +
                    "</pre>"
                );
            }
            reader.readAsText(file);
        }
    }
    function uploadProgress(evt) {
        if (evt.lengthComputable) {
            var percentComplete = Math.round(evt.loaded * 100 / evt.total);
            document.getElementById('progressNumber').innerHTML = percentComplete.toString() + '%';
        }
        else {
            document.getElementById('progressNumber').innerHTML = '';
        }
    }
    function UploadFile(file) {
        $id("filedrag").innerHTML = ""; //清空当前fileDrg的信息
        if (location.host.indexOf("sitepointstatic") >= 0) return
        var xhr = new XMLHttpRequest();
        if (xhr.upload && file.size <= $id("sizebyte").value && file.type == "image/jpeg") {
            var o = $id("progress");
            var progress = o.appendChild(document.createElement("p"));
//            progress.appendChild(document.createTextNode("名称： " + file.name));
//                        xhr.upload.addEventListener("progress", function (e) {
//                            var pc = parseInt(100 - (e.loaded / e.total * 100));
//                            progress.style.backgroundPosition = pc + "% 0";
//                        }, true);
            xhr.onreadystatechange = function (e) {
                alert(xhr.readyState);
                if (xhr.readyState == 4) {
                    progress.className = (xhr.status == 200 ? "success" : "failure");
                }
            };
            var files = file.name;
            FileName=file.name;
        }
    }
    $("#btnUpload").click(function () {
                if ($("#fileselect").val() == "") {
                 if(FileStr==""){
                    alert("请选择一个图片文件，再点击上传。");
                    return;
                    }else{
                        $.post(
                         "SaveServer.ashx",
                         {FileStr:FileStr},
                          function(data){
                            alert("成功");
                             $("#fileselect").val("");
                          }); 
                    }
                }else{ 
                $.post(
                         "SaveServer.ashx",
                         {FileStr:FileStr},
                          function(data){
                            alert("成功");
                             $("#fileselect").val("");
                             
                          });
                }
              
            });
    function Init() {
        var hh = this;
        var fileselect = $id("fileselect"),
            filedrag = $id("filedrag")/
            fileselect.addEventListener("change", FileSelectHandler, false);
           
        var xhr = new XMLHttpRequest();
        if (xhr.upload) {

            filedrag.addEventListener("progress", uploadProgress, false);
            filedrag.addEventListener("dragover", FileDragHover, false); //如果鼠标移动但停留在同一个控件中，则引发DragOver事件
            filedrag.addEventListener("dragleave", FileDragHover, false); //如果用户移出一个窗口，则引发DragLeave事件
            filedrag.addEventListener("drop", FileSelectHandler, false); //完成拖放操作
            filedrag.style.display = "block";
            upButton.style.display = "block";
        } 

    }
    if (window.File && window.FileList && window.FileReader) {
        Init();
    } else {
        upButton.style.display = "block";
        alert("您的浏览器不支持File API");
    }
})();

后台接受页面：
context.Response.ContentType = "text/plain";
            string[] aa = context.Request.Form["FileStr"].Split(',');
            MemoryStream ms = new MemoryStream(Convert.FromBase64String(aa[1]));
            Bitmap b = new Bitmap(ms);
            string serverPath = System.Web.HttpContext.Current.Server.MapPath("~");

            string toFilePath = Path.Combine(serverPath, @"imagesheadimg");
            string pach = toFilePath + GetImageName() + ".jpg";
            b.Save(pach);
            context.Response.Write("yes");
            context.Response.End();