if (DateTime.Compare(pt.EndTime, DateTime.Now) > 0)//时间对比
        {
              //pt.EndTime就是你数据库设置的结束时间
              //秒杀成功的处理代码
        }
        {
            ShowMessageBox("活动已结束，请关注下次活动！");
        }

------解决方案--------------------
HTML code
$(document).ready(function() {
  //电子电器
  var CountdownTImeE = $("input[id*=txtElectronCountdownTime]").val(); //倒计时

  if (CountdownTImeE != "" && CountdownTImeE != null) {
  var year = CountdownTImeE.split(' ')[0].split('-')[0]; //年
  var month = CountdownTImeE.split(' ')[0].split('-')[1]; //月
  var day = CountdownTImeE.split(' ')[0].split('-')[2]; //日
  var hour = CountdownTImeE.split(' ')[1].split(':')[0]; //时
  var min = CountdownTImeE.split(' ')[1].split(':')[1]; //分
  var second = CountdownTImeE.split(' ')[1].split(':')[2]; //秒
  var time = month + "/" + day + "/" + year + " " + hour + ":" + min + ":" + second;

  var endtime = new Date(time); //时间格式："7/21/2010 09:48:00"
  var nowtime = new Date();
  var maxtime = (endtime.getTime() - nowtime.getTime()) / 1000;

  var timer = setInterval("daojishiE()", 1000);

  if (maxtime <= 0) {

  $(".xs-qg-qw").eq(0).show();
  $(".xs-qg-qg").eq(0).hide();
  $(".xs-qg-qw").eq(1).show();
  $(".xs-qg-qg").eq(1).hide();
  clearInterval(timer);
  document.getElementById('showdateElectron').innerHTML = "<i>电子电器:</i><b>剩</b><em>00< /em><b>时</b><em>00</em><b>分< /b><em>00</em><b>秒</b>";
  }
  daojishiE = function() {
  if (maxtime >= 0) {
  //day = Math.floor(maxtime / 3600 / 24);
  hours = Math.floor(maxtime / 3600);
  minutes = Math.floor((maxtime / 60) % 60);
  seconds = Math.floor(maxtime % 60);
  msg = "<i>电子电器:</i><b>剩</b>" + "<em>" + hours + "</em>" + "<b>时</b>" + "<em>" + minutes + "</em>" + "<b>分</b>" + "<em>" + seconds + "</em>" + "<b>秒</b>";
  document.getElementById('showdateElectron').innerHTML = msg;
  //if(maxtime == 5*60) alert('注意，还有5分钟!');
  --maxtime;
  }
  else {

  var proid = "";
  $("#divCountdown input[id='hidProidE']").each(function() {
  proid += $(this).val() + ",";
  });
  $.get("/AjaxBehind/DefaultHandler.ashx", { type: "edit", proidlist: proid }, function(data) {
  $("#showdateElectron").html(data);
  clearInterval(timer);
  window.location = window.location;
  });

  }
  }
  }
});