asp.net 服务器控件 JS验证

`
//使用
OnClientClick="return checkselect()"

function checkselect() {

            //验证下拉必选
            var value = document.getElementById("ddlWorkType").value;            
            if (value == "0") {                
                document.getElementById("Label1").innerText = "请选择 选择工种！";
                return false;
            }

            //验证非空
            value = document.getElementById("txtorgcode").value;
            if (value == "") {
                alert("组织机构代码 不能为空！");
                return false;
            }

            //正则验证
            var Regex = /^(?:w+.?)*w+@(?:w+.)*w+$/;
            value = document.getElementById("txtemail").value;
            if (!Regex.test(value)) {
                alert("电子邮件格式不正确，请重新输入。如：tkb@126.com");
                document.getElementById("txtemail").value = "";
                return false;
            }

            //列表选择
            var GridView1 = document.getElementById("<%=GVListShow.ClientID %>");
            var seleccheck = false;
            for (i = 1; i < GridView1.rows.length; i++) {
                if (GridView1.rows[i].cells[0].getElementsByTagName("INPUT")[0].checked) {
                    seleccheck = true;
                    break;
                }
            }
            if (!seleccheck) {               
                document.getElementById("Label1").innerText = "请选择 报名人员！"; 
                return false;
            }

            //下拉列表
            var CheckBox = document.getElementById("<%=ddlCompanyType.ClientID%>").getElementsByTagName("INPUT");
            if (CheckBox != undefined) {
                var j = 0;
                for (var i = 0; i < CheckBox.length; i++) {
                    if (CheckBox[i].checked) {
                        j += 1;
                    }
                }
                if (j == 0) {
                    alert("请选择，企业类型！");
                    return false;
                }
            }
        }`