多文件上传
首先HTML 源文件中 添加文件上传Html组件

<script language="javascript" type="text/javascript">
function addFile()
{
     //添加文件上传Html组件
      var str ='<input type="file" name="File" /></br>'
      document.getElementById('MyFile').insertAdjacentHTML("beforeEnd",str)
}
</script>
后台:
   HttpFileCollection files = HttpContext.Current.Request.Files;

   for (int iFile = 0; iFile < files.Count; iFile++)
   {          
            HttpPostedFile postedFile = files[iFile];
            string fileName, fileExtension;
            fileName = System.IO.Path.GetFileName(postedFile.FileName);
            if (fileName != "")
            {
                fileExtension = System.IO.Path.GetExtension(fileName);         
                postedFile.SaveAs(System.Web.HttpContext.Current.Request.MapPath("Fll/") + fileName);
            }
   }
   Response.Write("文件上传成功!");

当遇到大文件上传需要修改配置文件:

<httpRuntime useFullyQualifiedRedirectUrl="true" maxRequestLength="1024000" executionTimeout="900"/>