string cnnString = GetConnectionString();
            SqlConnection connection = new SqlConnection(cnnString);
            {
                try
                {
                    switch (connection.State)
                    {
                        case ConnectionState.Open:
                            connection.Close();
                            lbCnn.Text = "Подключено";
                            btnConnect.Text = "Отключить";
                            break;
                        case ConnectionState.Closed:
                            connection.Open();
                            lbCnn.Text = "Отлючено";
                            btnConnect.Text = "Подключить";
                            break;


                        default: MessageBox.Show("Неопределённое состояние подключения!");
                            break;
                    }
                  
                }
                catch (Exception err)
                {
                    MessageBox.Show("Ошибка подключения: " + err);
                    string LogPath = @"\windows\flylog.txt";
                    using (StreamWriter sw = File.CreateText (LogPath)) {
                        sw.WriteLine (err);
                    }
                    
                }
            }

        }

        static private string  GetConnectionString () {
            return  "Data Source=PPL-SQL-058;Initial Catalog=test;User ID=Fly;Password=_passwd_"; 
        }