提交按钮，有时执行了page_load事件，但不执行click事件，

如题，这个问题不是一直都有，有时提交会进入click事件，有时又不会了，概率还挺高的。<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Login.aspx.cs" Inherits="Login" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>登录</title>
    <style type="text/css">
        body
        {
            font: 14px/1.2 "微软雅黑";
        }
        
        #regContainer
        {
            width: 300px;
            position: relative;
            margin: 20px 0;
            padding: 5px 10px;
        }
        
        .form_control
        {
            border: 1px #ccc solid;
        }
        
        input[type="text"], input[type="password"]
        {
            border: none;
            width: 100%;
        }
        
        .form_control.active
        {
            border: 1px #32BC61 solid;
            background-color: #fff;
        }
        
        label.error
        {
            background: url("res/js/validate/images/unchecked.gif") no-repeat 0px 0px;
            padding-left: 16px;
            padding-bottom: 2px;
            font-weight: bold;
            color: #EA5200;
        }
        label.checked
        {
            background: url("res/js/validate/images/checked.gif") no-repeat 0px 0px;
        }
    </style>
</head>
<body>
    <form id="form1" runat="server">
    <div id="regContainer">
        <p style="text-align: center; font-size: 16px;">
            会员登录</p>
        <div class="form_control">
            用户名：
            <input value="" type="text" id="txtPhone" name="txtPhone">
        </div>
        <div class="form_control">
            密 码：
            <input value="" type="password" name="txtPwd" id="txtPwd">
        </div>
        <div class="form_control">
            验证码：
            <input value="" type="text" id="txtCode" name="txtCode" style="width: 80px;"><img
                align="absmiddle" class="imgcode" src="checkcode.ashx" style="cursor: pointer;"
                onclick="this.src=this.src+'?'" />
        </div>
        <div>
            <asp:HiddenField ID="hfValue" runat="server" />
            <asp:Button ID="btnLogin" runat="server" Text="登录" onclick="btnLogin_Click"/>
        </div>
    </div>
    <script src="res/js/jquery.js"></script>
    <script src="res/js/validate/jquery.validate.min.js"></script>
    <script src="res/js/validate/my-methods.js"></script>
    <script src="res/js/layer2.1/layer.js"></script>
    <script>
        $(function () {            $("#form1").validate({
                rules: {
                    txtPhone: {
                        required: true,
                        Tel: true
                    },
                    txtPwd: {
                        required: true,
                        minlength: 6,
                        maxlength: 16
                    },
                    txtCode: {
                        required: true,
                        minlength: 4,
                        maxlength: 4,
                        remote: {
                            url: "ajax/CheckLoginCode.ashx",
                            type: "post",
                            dataType: "json",
                            data: {
                                code: function () { return $("#txtCode").val(); }
                            },
                            dataType: "html",
                            dataFilter: function (data, type) {
                                // alert(data);
                                if (data == "true")
                                    return true;
                                else
                                    return false;
                            }
                        }                    }
                },
                messages: {
                    txtPhone: {
                        required: "请输入手机号码",
                        Tel: "手机号码格式不正确"                    },
                    txtPwd: {
                        required: "请输入密码",
                        minlength: "密码长度不能小于6个字符",
                        maxlength: "密码长度不能大于16个字符"
                    },
                    txtCode: {
                        required: "请输入验证码",
                        minlength: "验证码是4位数字",
                        maxlength: "验证码是4位数字",
                        remote: "验证码输入不正确"
                    }
                }
            });
        });
    </script>
    </form>
</body>
</html>public partial class Login : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {    }    
    protected void btnLogin_Click(object sender, EventArgs e)
    {
        string mobile = Request.Form["txtPhone"].ToStr();
        string pwd = Request.Form["txtPwd"].ToStr();
        string code = Request.Form["txtCode"].ToStr();
        string checkCode = Session["codesession"].ToStr();
      
        //手机号为空
        if (string.IsNullOrEmpty(mobile))
        {
            JsHelper.AlertError("请输入手机号！");
            return;
        }
       
        //密码为空
        if (string.IsNullOrEmpty(pwd))
        {
            JsHelper.AlertError("请输入密码！");
            return;
        }
               //验证码为空
        if (string.IsNullOrEmpty(code))
        {
            JsHelper.AlertError("请输入验证码！");
            return;
        }
              //验证码输入不正确
        if (!checkCode.Equals(code, StringComparison.OrdinalIgnoreCase))
        {
            JsHelper.AlertError("验证码不正确！");
            return;
        }
        Response.Write("<script>alert('5');</script>");        string flag = LoginHelper.LoginByMobile(mobile, pwd, false);
      
        switch (flag)
        {
            default:
            case "0": //用户名或密码错误
            case "3": //帐号已删除到回收站
                JsHelper.AlertError("用户名或密码错误！");
                break;
            case "1": //帐号未审核
                JsHelper.AlertError("帐号审核中，请等待！");
                break;
            case "2": //登录成功
                JsHelper.AlertSuccess("登录成功", "member/success.aspx");
                break;        }
    }
}