如何实现多个文件的上传

一般怎么实现，后台怎么反馈进度给前端以实现进度条的功能。
讲讲实现原理~我现在的方法：渣到不行 抛砖引玉吧html：  <table id="imageUploadtable">
                  <tr> 
                 <td><a onclick="addFile()" style="cursor:pointer">点击添加文件</a></td>
                  </tr>
                  <tr id="tr_file0">
                  <td>证件类型:</td>
                  <td><select id="documenttype0" name="documenttype0"></select> </td>
                  <td><input type="file" id="file0" name="file0"/><span id="span_file0"></span><span id="del_file0"></span></td>
                  </tr>
                  </table>
JS：  var __FILE_INDEX =0;
    function addFile() {
        ++__FILE_INDEX;
        var fileId = "file" + __FILE_INDEX;
        var uploadTable = document.getElementById("imageUploadtable")
        var trElement = uploadTable.insertRow(-1);
        trElement.id = "tr_" + fileId;
        var tdElement = trElement.insertCell(-1);
        tdElement.id = "td_" + fileId;
        tdElement.innerHTML = "<input type='file' name='" + fileId + "' id='" + fileId + "' size='30' style='padding-left:5px;width:300px;cursor:pointer;' >"
               + "<span id='span_" + fileId + "'></span>"
               + "<span id='del_" + fileId + "'></span>";
        var lasttrid = "file" + (__FILE_INDEX-1).toString();        document.getElementById("del_" + lasttrid).innerHTML = "<span title='删除文件' onclick='deleteFile(\"" + lasttrid + "\")' style='font-size:12px;color: #4684b2;cursor:pointer;border-bottom:1px solid #4684b2'>删除</span>";
    }    function deleteFile(fileId) {
        var trNode = document.getElementById("tr_" + fileId);
        var trParent = trNode.parentNode;
        trParent.removeChild(trNode);
    }C#:
for (int i = 0; i < Request.Files.Count; i++)
                    {
                        if (Request.Files[i] != null)
                        {
                            HttpPostedFile filePost = Request.Files[i];
                            string filename = filePost.FileName;
                            Random rd = new Random();
                            filename = filename.Substring(filename.LastIndexOf('\\') + 1);
                            string savePath = Server.MapPath("UpLoadFile/" + rd.Next() + filename);
                            filePost.SaveAs(savePath);
         
                        }               
                    }一个下拉框跟一个file控件如何对应起来，
request.File[i]索引是按何种顺序索引的？是按前台的html的顺序吗？