private void btnLogIn_Click(object sender, EventArgs e)
        {
            if (tbLog.Text != "")
            {
                if (tbPass.Text != "")
                {
                    var sqlconection = new SqlConnection(ConnectionString);
                    using (sqlconection)
                    {
                        sqlconection.Open();
                        var command = new SqlCommand
                        {
                            Connection = sqlconection,
                            CommandText = "SELECT * FROM Login WHERE Login.Login= '******'",
                            CommandType = CommandType.Text
                        };

                        SqlDataReader dr = command.ExecuteReader();
                        if (dr.Read())
                        {
                            string log = dr[0].ToString();
                            string pass = dr[1].ToString();
                            if (pass == tbPass.Text)
                            {
                                bool adm = Convert.ToBoolean(dr[2]); Main newMain = new Main(adm, log);
                                appendText = DateTime.Now.ToString() + ": пользователь " + log + " вошел в систему.\n";
                                File.AppendAllText(path, appendText, Encoding.UTF8);
                                newMain.Show(); this.Hide();
                            }
                            else
                            {
                                tbPass.Clear();
                                lblErrPass.Text = "Неверный пароль";
                            }
                        }
                        else
                        {
                            tbLog.Clear();
                            tbPass.Clear();
                            lblErrLog.Text = "Неверный логин";
                        };
                        dr.Close();
                    }
                }
                else { lblErrPass.Text = "Введите пароль";}
            }
            else { lblErrLog.Text = "Введите логин"; }
        }
 private void frmAdd_FormClosed(object sender, FormClosedEventArgs e)
 {
     Main newMain = new Main(true, log);
     newMain.Show();
 }