C#简单验证并限制登录次数小示例

描述：提示用户输入用户名，密码，与数据库中的数据匹配，如果正确则提示登陆成功，否则，提示登陆失败 错误次数超过三次，提示登陆次数过多，禁止登陆

数据表示例：

//数据库中ErrorTimes的次数增加1
public void incError()
        {
            using (SqlConnection conn = new SqlConnection(@"Data Source=.SQLEXPRESS;AttachDBFilename=|DataDirectory|Database1.mdf;Integrated Security=True;User Instance=True"))
            {
                conn.Open();
                SqlCommand cmd1 = conn.CreateCommand();
                cmd1.CommandText = "update T_Users set ErrorTimes=ErrorTimes+1 where UserName=@UN";
                cmd1.Parameters.Add(new SqlParameter("UN", txtUsername.Text));
                cmd1.ExecuteNonQuery();
                 
            }
        }
//重置数据库中ErrorTimes的次数为0
        public void clsError()
        {
            using (SqlConnection conn = new SqlConnection(@"Data Source=.SQLEXPRESS;AttachDBFilename=|DataDirectory|Database1.mdf;Integrated Security=True;User Instance=True"))
            {
                conn.Open();
                SqlCommand cmd1 = conn.CreateCommand();
                cmd1.CommandText = "update T_Users set ErrorTimes=0 where UserName=@UN";
                cmd1.Parameters.Add(new SqlParameter("UN", txtUsername.Text));
                cmd1.ExecuteNonQuery();
 
            }
 
       private void button1_Click(object sender, EventArgs e)
        {
            //提示用户输入用户名，密码，与数据库中的数据匹配，如果正确则提示登陆成功，否则，提示登陆失败
            ///错误次数超过三次，提示登陆次数过多，禁止登陆。
            using (SqlConnection conn = new SqlConnection(@"Data Source=.SQLEXPRESS;AttachDBFilename=|DataDirectory|Database1.mdf;Integrated Security=True;User Instance=True"))
            {
                conn.Open();
                SqlCommand cmd = conn.CreateCommand();
                cmd.CommandText = "select * from T_Users where UserName=@UN";
                cmd.Parameters.Add(new SqlParameter("UN", txtUsername.Text));
                using (SqlDataReader reader = cmd.ExecuteReader())
                {
                    if (reader.Read())
                    {
                        int errortimes = reader.GetInt32(reader.GetOrdinal("ErrorTimes"));
                        if (errortimes > 3)
                        {
                            MessageBox.Show("错误次数过多，禁止登陆");
                        }
                        string dbpassword = reader.GetString(reader.GetOrdinal("PassWord"));
                        if (dbpassword == txtPassword.Text)
                        {
                            MessageBox.Show("登陆成功");
                            clsError();
                        }
                        else
                        {
                            incError();
                            MessageBox.Show("登陆失败");
                            
                        }
                    }
                    else
                    {
                        MessageBox.Show("用户名不存在");
                    }