上传多张图片用Session临时存储

  DataTable dtImages = new DataTable();
            string filepath = FileUpload1.PostedFile.FileName;
            //检查是否有文件要上传  
            if (this.FileUpload1.HasFile)
            {
                if (this.FileUpload1.PostedFile.ContentLength > 3096000)
                {
                    webmsg.message("文件不能超过3M!");
                    return;
                }

                filepath = FileUpload1.FileName;
                string filetype = System.IO.Path.GetExtension(filepath).ToLower();//获得后缀名  
                if (filetype == ".jpg" || filetype == ".png" || filetype == ".gif")
                {
                    DateTime dt = DateTime.Now;
                    string filename = string.Format("{0:yyyyMMddHHmmssffff}", dt) + filetype;

                    string savepath = Server.MapPath("../StudentCenter/Upload/") + filename;
                    FileUpload1.PostedFile.SaveAs(savepath);

                    string imgurl = "../StudentCenter/Upload/" + filename;

                    if (Session["UPLOAD"] == null)
                    {
                        dtImages.Columns.Add("imgUrl", typeof(object));
                        dtImages.Rows.Add(new object[] { imgurl });
                        Session["UPLOAD"] = dtImages;
                    }
                    else
                    {
                        dtImages = Session["UPLOAD"] as DataTable;
                        dtImages.Rows.Add(new object[] { imgurl });
                        Session["UPLOAD"] = dtImages;
                    }

                    dlst_img.DataSource = Session["UPLOAD"];
                    dlst_img.DataBind();
                }
                else
                {
                    webmsg.message("请上传jpg或png或gif的图片格式!");
                }
            }