定义下拉框：

 <div class="layui-inline">
                        <label class="layui-form-label " style="width:120px">督学主题：</label>
                        <div class="layui-input-inline">
                            <select id="ThremeType" name="ThremeType" lay-filter="Thremetype">
                                @foreach (var item in ViewBag.Threme)
                                {
                                    <option value="@item.Id">@item.Name</option>
                                }
                            </select>
                        </div>
                    </div>

JS取值：

let schooltype =$("#ThremeType").val();

获取一个下拉框的值，和之前一篇动态加载后台数据显示到下拉框里面对应

Layui动态从数据库获取下拉框列表：https://blog.csdn.net/weixin_42189604/article/details/88797833

HTML:

<select name="sex" lay-filter="sex">
	<option value="1">男</option>
	<option value="2" selected>女</option>
</select>

JS:

form.on('select(sex)', function (data) {        //对应lay-filter
		sex= data.value;                                   //获取value值
		text= data.elem[data.elem.selectedIndex].text;;    //获取显示的值
		
});