private void buttonLogIn_Click(object sender, EventArgs e) { // store employees email for later use string employeeEmail = comboBoxEmail.Text; // validate email and store any error messages received string errorMessage = LoginValidation.ValidateEmail(comboBoxEmail.Text); // if error message returned, turn the flag on if (!string.IsNullOrWhiteSpace(errorMessage)) { errorProvider.SetError(comboBoxEmail, errorMessage); return; } // check if password was not left blank before continuing if (string.IsNullOrWhiteSpace(textBoxPassword.Text)) { errorProvider.SetError(textBoxPassword, "Password must not be left blank!"); return; } // store results of validation as boolean values (bool emailValid, bool passwordValid) var(emailValid, passwordValid) = LoginValidation.ValidateCredentials(employeeEmail, textBoxPassword.Text); // if both email and password are valid, continue to main application if (emailValid && passwordValid) { // add logon entry to log file FileWriter.WriteLog("login"); // if email address already occurs in the log file, delete it FileWriter.DeleteLine(MAIL_LOG_FILE, FileWriter.ContainsLine(MAIL_LOG_FILE, employeeEmail)); // insert email address at the beginning of the file FileWriter.InsertAtBeginning(MAIL_LOG_FILE, employeeEmail); // hide current form this.Hide(); // create main form and open it using (Main MainApplication = new Main(employeeEmail)) MainApplication.ShowDialog(); // once main application closes, add logoff entry to event file FileWriter.WriteLog("logout"); // open login page again this.Show(); // load default settings of the login page LoadDefaultSettings(); } // else if email incorrect else if (!emailValid) { errorProvider.SetError(comboBoxEmail, "Email address incorrect!"); } // else if password incorrect else if (!passwordValid) { errorProvider.SetError(textBoxPassword, "Password incorrect!"); } // in case of any inexpected errors else { FileWriter.WriteLog("login validation error"); MessageBox.Show("Please report this error to your manager.", "Unexpected Error"); } }