Dim txt As String
        Dim wb As New WeUI
        wb.AddPageTitle("","pt1",_xitongname,"用户工单")
        wb.AddForm("","form1","yonghugongdanjieguo.htm")
        Dim pps As List(of String) = DataTables("基础信息").GetValues("一类","名称 = \'品牌种类\'","排序")
        With wb.AddInputGroup("form1","ig1","基本信息")
            .AddSelect("产品品牌","产品品牌","|" & String.Join("|",pps.ToArray)).Attribute = ""    ""
            .AddSelect("产品种类","产品种类","")
        End With
        \'wb.InsertHTML("<style>#ig1{font-family:\'微软雅黑\';font-size:25px}</style>") \'设置字体
        wb.InsertHTML("<div style=\'height:100px\'></div>")
        wb.AddPage("form1","page1").Attribute = "style=\'position: fixed;bottom: 0;right: 0;left: 0\'"
        With wb.AddButtonGroup("page1","btg1", False)
            .Add("btn1", "确定上报","submit").Attribute = ""  ""  ‘不显示的，就是单击时间调用下面的函数
        End With
        \'给产品种类
        For Each pp As String In pps
            \'插入一些隐藏段落,用于存储各个国家的汽车品牌
            wb.InsertHTML("<p hidden id=\'" & pp & "\'>" & DataTables("基础信息").GetComboListString("二类","名称 = \'品牌种类\' and 一类 = \'" & pp & "\'","排序") & "</p>")
        Next
        wb.AppendHTML("<script src=\'./lib/chanpin.js\'></script>") \'引入脚本文件 品牌种类
        wb.AppendHTML("<script src=\'./lib/kongzhi.js\'></script>") \'引入脚本文件 空值判断
        e.WriteString(wb.Build)

function getyonghugongdan() {
 var txt = document.getElementById("产品品牌").value;
 if (txt == "") {
  alert("产品品牌不能为空");
 }
}

有两个问题，一个是提示框有域名体验不好

另一个是如果为空不知怎么中止转到下一界面，如果为空是不做任何操作的需要再当前页面继续录入数据