Jquery实现异步上传图片

html xmlns="http://www.w3.org/1999/xhtml">
head id="Head1" runat="server">
    title>title>
    script src="Scripts/jquery-1.3.2-vsdoc2.js" type="text/javascript">script>
    script type="text/javascript">
        function uploadImage() {
        //判断是否有选择上传文件
            var imgPath = $("#uploadFile").val();
            if (imgPath == "") {
                alert("请选择上传图片！");
                return;
            }
            //判断上传文件的后缀名
            var strExtension = imgPath.substr(imgPath.lastIndexOf(‘.‘) + 1);
            if (strExtension != ‘jpg‘ && strExtension != ‘gif‘
            && strExtension != ‘png‘ && strExtension != ‘bmp‘) {
                alert("请选择图片文件");
                return;
            }
            $.ajax({
                type: "POST",
                url: "handler/UploadImageHandler.ashx",
                data: { imgPath: $("#uploadFile").val() },
                cache: false,
                success: function(data) {
                    alert("上传成功");
                    $("#imgDiv").empty();
                    $("#imgDiv").html(data);
                    $("#imgDiv").show();
                },
                error: function(XMLHttpRequest, textStatus, errorThrown) {
                    alert("上传失败，请检查网络后重试");
                }
            });
        }
    script>
head>
body>
form  enctype="multipart/form-data" method="post">
input type="file" id="uploadFile" runat="server" />
input type="button" id="btnUpload" value="确定" onclick="uploadImage()" />
div id="imgDiv">
div>
form>
body>
html>

    public void ProcessRequest (HttpContext context) {
        //不知道为什么获取不到
        //HttpPostedFile file = context.Request.Files["userFile"];
        string filePath = context.Request["imgPath"];
        string path = "UploadImgs\\";
        Bitmap map = new Bitmap(filePath);
        string fileName = Path.GetFileName(filePath);
        string mapPath = context.Server.MapPath("~");
        string savePath = mapPath + "\\" + path + fileName;
        map.Save(savePath);
        //上传成功后显示IMG文件
        StringBuilder sb = new StringBuilder();
        sb.Append(""+path.Replace("\\","/")+fileName+"\" />");
        context.Response.Write(sb.ToString());
        context.Response.End();
    }
 
    public bool IsReusable {
        get {
            return false;
        }
    }