附件，图片等上传代码

<!--Html-->
<td colspan="2"><input  type='file' name='txfile' require='true' datatype='require' style="width:468px;" class="write_3" />

 HttpPostedFile tx = Request.Files["txfile"];
if (tx.FileName != null && tx.FileName.ToString() != "")
                    {
                        if (tx.ContentLength > 1024 * 50)
                        {
                            base.Alert("上传图标不能超过50KB");
                            return;
                        }
                        oldtx = UpLoad(tx);

                    }
//method
  public string UpLoad(HttpPostedFile hpf)
        {
            string strExt = hpf.FileName.Remove(0, hpf.FileName.LastIndexOf("."));
            string[] Er = { ".jpg", ".png", ".bmp" };
            string lower = strExt.ToLower();
            int len = Er.Length;
            bool btrue = false;
            for (int num = 0; num < len; num++)
            {
                if (lower == Er[num])
                {
                    btrue = true;
                }
            }
            if (!btrue)
            {
                //"图标格式不正确，请上传图标";
                return "";
            }

            Random ra = new Random();
            DateTime datNow = DateTime.Now;
            string MyFileName = datNow.Year.ToString() + datNow.Month.ToString() + datNow.Day.ToString() + datNow.Hour.ToString() + datNow.Minute.ToString() + datNow.Second.ToString() + datNow.Millisecond.ToString();
            string strNewName = MyFileName + ra.Next(10000) + hpf.FileName.Remove(0, hpf.FileName.LastIndexOf("."));//文件名
            string strpath = Server.MapPath("~/UploadFiles/affix/") + strNewName;
            hpf.SaveAs(strpath);
            return "/UploadFiles/affix/" + strNewName;//相对路径
        }