html5 新特性      <input id="imgsf" type="file" name="imgsf" multiple  />    input  file 中增加 multiple   属性可以选择多文件。IE9以下版本不兼容          <form id="form1" method="post" action="upload_json.ashx" enctype="multipart/form-data">      <div>       <input id="imgsf" type="file" name="imgsf" multiple  />          <input type="text" name="ceshi" value="panlitao" >          <input type="submit" value="提交" />      </div>      </form>      //预览js      <div id="imgrq">      </div>       <script type="text/javascript">                      $("#imgsf").change(function () {               var filedx = 0;               for (var i = 0, j = this.files.length; i < j; i++) {                   $("#imgrq").append("<img  src=\"" + window.URL.createObjectURL(this.files[i]) + "\" width=\"100\" height=\"100\" />");               }               });          </script>    C# 代码     public class upload_json : IHttpHandler      {         // private HttpContext context;              public void ProcessRequest(HttpContext context)          {              String aspxUrl = context.Request.Path.Substring(0, context.Request.Path.LastIndexOf("/") + 1);                  //文件保存目录路径              String savePath = "attached/";                  //文件保存目录URL              String saveUrl = aspxUrl + "attached/";                  //定义允许上传的文件扩展名              Hashtable extTable = new Hashtable();              extTable.Add("image", "gif,jpg,jpeg,png,bmp");              //extTable.Add("flash", "swf,flv");              //extTable.Add("media", "swf,flv,mp3,wav,wma,wmv,mid,avi,mpg,asf,rm,rmvb");              //extTable.Add("file", "doc,docx,xls,xlsx,ppt,htm,html,txt,zip,rar,gz,bz2");                  //最大文件大小              int maxSize = 1000000;            //  this.context = context;              String newFileName = "";              for (int i = 0; i < context.Request.Files.Count;i++ )              {                  HttpPostedFile imgFile = context.Request.Files[i];                                         if (imgFile == null)                  {                      showError("请选择文件。");                  }                      String dirPath = context.Server.MapPath(savePath);                  if (!Directory.Exists(dirPath))                  {                      showError("上传目录不存在。");                  }                      String dirName = context.Request.QueryString["dir"];                  if (String.IsNullOrEmpty(dirName))                  {                      dirName = "image";                  }                  if (!extTable.ContainsKey(dirName))                  {                      showError("目录名不正确。");                  }                      String fileName = imgFile.FileName;                  String fileExt = Path.GetExtension(fileName).ToLower();                      if (imgFile.InputStream == null || imgFile.InputStream.Length > maxSize)                  {                      showError("上传文件大小超过限制。");                  }                          //修改为文件流去判断文件格式                  // string exPath = mall_bll.Common.isfilltype(stream: imgFile.InputStream).ToLower();                      //  if (exPath != "jpg" && exPath != "gif" && exPath != "bmp" && exPath != "png")                  //   { showError("上传文件扩展名是不允许的扩展名。\n只允许" + ((String)extTable[dirName]) + "格式。"); }                      //if (String.IsNullOrEmpty(fileExt) || Array.IndexOf(((String)extTable[dirName]).Split(','), fileExt.Substring(1).ToLower()) == -1)                  //{                  //    showError("上传文件扩展名是不允许的扩展名。\n只允许" + ((String)extTable[dirName]) + "格式。");                  //}                      //创建文件夹                  dirPath += dirName + "/";                  saveUrl += dirName + "/";                  if (!Directory.Exists(dirPath))                  {                      Directory.CreateDirectory(dirPath);                  }                  String ymd = DateTime.Now.ToString("yyyyMMdd", DateTimeFormatInfo.InvariantInfo);                  dirPath += ymd + "/";                  saveUrl += ymd + "/";                  if (!Directory.Exists(dirPath))                  {                      Directory.CreateDirectory(dirPath);                  }                       newFileName = DateTime.Now.ToString("yyyyMMddHHmmss_ffff", DateTimeFormatInfo.InvariantInfo) + fileExt;                  String filePath = dirPath + newFileName;                      imgFile.SaveAs(filePath);              }              String fileUrl = saveUrl + newFileName;                  Hashtable hash = new Hashtable();              hash["error"] = 0;              hash["url"] = fileUrl;              context.Response.AddHeader("Content-Type", "text/html; charset=UTF-8");           //   context.Response.Write(JsonMapper.ToJson(hash));              context.Response.End();          }              private void showError(string message)          {              Hashtable hash = new Hashtable();              hash["error"] = 1;              hash["message"] = message;           //   context.Response.AddHeader("Content-Type", "text/html; charset=UTF-8");           //   context.Response.Write(JsonMapper.ToJson(hash));         //     context.Response.End();          }              public bool IsReusable          {              get              {                  return true;              }          }      }