请教

代码如下，运行后我的按钮不起作用。这是怎么回事？初学，谢谢大家了
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using MySql.Data;namespace login
{    public partial class frmLogin : Form
    {
        private int nLoginCount = 0;
        private const int MAX_LOGIN_COUNT = 3;        private UserInfo uiLogin;        public frmLogin(ref UserInfo ui)
        {
            InitializeComponent();
            uiLogin = ui;
        }        private void btnOK_Click(object sender, EventArgs e)
        {
            // 用户名和密码
            // 从数据库读取用户名和密码(还没写额)            if (txtUserName.Text == "admin" && txtPassword.Text == "admin")
            {
                // 保存登录信息
                uiLogin.UserName = txtUserName.Text;
                uiLogin.Password = txtPassword.Text;                // 设定会话结果
                this.DialogResult = DialogResult.OK;
            }
            else
            {
                // 错误的用户名称或密码
                nLoginCount++;
                if (nLoginCount == MAX_LOGIN_COUNT)
                    // 超过 3次
                    this.DialogResult = DialogResult.Cancel;
                else
                {
                    MessageBox.Show("用户名或密码错误");
                    txtUserName.Focus();
                }
            }        }        private void btnCancel_Click(object sender, EventArgs e)
        {
            this.DialogResult = DialogResult.Cancel;        }        private void frmLogin_FormClosing(object sender, FormClosingEventArgs e)
        {
            // 检查是否与对话的形式而需要关闭
            if (this.DialogResult != DialogResult.Cancel &&
                this.DialogResult != DialogResult.OK)
                e.Cancel = true;        }        private void frmLogin_Load(object sender, EventArgs e)
        {
            this.AcceptButton = this.btnOK;
            this.CancelButton = this.btnCancel;
            this.txtUserName.Focus();//刷新用户名框光标定位在此
        }
            }
}