在使用jQuery ajax 上传图片时，下载一个ajaxfileupload.js包，利用ajax和一般处理程序完成文件的上传，这样获取图片路径、上传图片就比较快捷

（一般处理程序）

　　 public void ProcessRequest(HttpContext context)
        {
            context.Response.ContentType = "text/plain";
            string filePath = "";
            string msg = "";
            string fileNewName = "";
            string result = string.Empty; //也是定义一个空变量
            string fileNewPath = string.Empty;
            //接收文件
            HttpFileCollection files = context.Request.Files;
            //判断是否获取到文件
            if (files.Count > 0)
            {
                //设置图片名称
                //DateTime.Now.ToString("yyyyMMddHHmmssff")
                fileNewName = Guid.NewGuid() + "_" + Path.GetFileName(files[0].FileName);
                //保存文件
                files[0].SaveAs(context.Server.MapPath("~/Upload/" + fileNewName));
                msg = "图片上传成功";
                fileNewPath = "Upload/" + fileNewName;
                result = "{msg:'" + msg + "',fileNewPath:'" + fileNewPath + "'}"
               
            }
            else
            {
                msg = "图片上传失败";
                result = "{msg:'" + msg + "'}";
            }
            context.Response.Write(result);
            context.Response.End();
        }

 <script type="text/javascript">
        $(function () {
            $(".file").on("change", "input[type='file']", function () {
                var filePath = $(this).val();
                //设置上传文件的类型
                if (filePath.indexOf("xls") != -1 || filePath.indexOf("xlsx") != -1 || filePath.indexOf("jpg") != -1) {
                    alert(111);
                    //执行上传文件的操作
                    $.ajaxFileUpload({
                        url: "UploadHandler.ashx", //   请求地址
                        secureuri: false, // 是否开启安全提交，默认为false
                        fileElementId: "btnfile", //需要上传的文件域的ID 也就是 <input type="file" id="btnfile" name="btnfile" />里面的id
                        dataType: "json", //制定返回数据类型（json,html，xml,script） 如果不写，jquery会自动判断
                        success: function (data) {  //执行成功之后自动执行的函数
                            console.log(data);
                            alert(data.msg);
                            $("#txt_filepath").val(data.fileNewPath);
                            $("#hImg").prop("src", data.fileNewPath);

                        },
                        error: function (data) { //执行失败之后自动执行的函数
                            console.log(data);
                        }
                    })
                }
                else {
                    alert("请选择正确格式的文件");
                }
            })
        })
    </script>

 <form id="form1" runat="server">
        <div>
            <span>选择文件：</span>
            <input type="text" readonly="readonly" id="txt_filepath" />
            <a class="file">
                <input type="file" id="btnfile" name="btnfile" />
                浏览文件
            </a>
            <img style=" 300px; height: 300px;" id="hImg" />
        </div>