$(function () {    $("#btn").click(function () {      var usercode = $("#UserCode").val();      var verifycode = $("#Verifycode").val();      if ($.trim(usercode) == "" || $.trim(verifycode) == "") {        alert(" 您的[客戶號]或者[驗證碼]必須填寫！");        return false;      }      else {        document.SearchForm.action = '/index/Search?u=' + usercode;        document.SearchForm.submit();      }    });  });

<form id="SearchForm" name="SearchForm" method="post"> ……</form>