try
            {
                DataTable dt = new DataTable();
                dt = SQLHelp.ExecuteDataTable("select * from t_user where UserName=@name", new SqlParameter("name", txtUserName.Text));
                if (dt.Rows.Count < 0)
                {
                    MessageBox.Show("用户不存在");
                    return;
                }
                else
                {
                    if (Convert.ToInt32(dt.Rows[0]["ErrorTimes"]) < 3)
                    {
                        if (txtPassword.Text == dt.Rows[0]["Password"].ToString())
                        {
                            SQLHelp.ExecuteNonQuery("update t_user set ErrorTimes=0 where UserName=@name", new SqlParameter("name", txtUserName.Text));

                            if (MessageBox.Show("登录成功") == DialogResult.OK)
                            {
                                this.DialogResult = DialogResult.OK;
                                this.Close();
                            }
                        }
                        else
                        {
                            SQLHelp.ExecuteNonQuery("update t_user set ErrorTimes=ErrorTimes+1 where username=@name", new SqlParameter("name", txtUserName.Text));
                            MessageBox.Show("密码错误");
                        }
                    }
                    else
                    {
                        MessageBox.Show("登录次数超过3次，用户被禁止登录");
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }