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 > )
                         {
                             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");
                     }