private void Create_Click(object sender, EventArgs e) { if (Regex.IsMatch(nameBox.Text, pattern: @"^[a-zA-ZąčęėįšųūžĄČĘĖĮŠŲŪŽ]+$")) { nameBox.BackColor = Color.LightGreen; } else { nameBox.BackColor = Color.Salmon; } if (Regex.IsMatch(lastNameBox.Text, pattern: @"^[a-zA-ZąčęėįšųūžĄČĘĖĮŠŲŪŽ]+$")) { lastNameBox.BackColor = Color.LightGreen; } else { lastNameBox.BackColor = Color.Salmon; } if (Regex.IsMatch(telNumberBox.Text, pattern: @"^(?!\s*$)[0-9]{8,14}$")) { telNumberBox.BackColor = Color.LightGreen; } else { telNumberBox.BackColor = Color.Salmon; } if (Regex.IsMatch(emailBox.Text, pattern: @"[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?")) { emailBox.BackColor = Color.LightGreen; } else { emailBox.BackColor = Color.Salmon; } if (nameBox.BackColor == Color.LightGreen && lastNameBox.BackColor == Color.LightGreen && telNumberBox.BackColor == Color.LightGreen && emailBox.BackColor == Color.LightGreen) { if (DatabaseMethods.SelectClients().Select(x => x.Email).ToList().Contains(emailBox.Text)) { MessageBox.Show("This email address exists!", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); } else { Client client = new Client(nameBox.Text, lastNameBox.Text, emailBox.Text, telNumberBox.Text, new List <ILogger> { new LogFileWritter(), new ScreenObjectInfoWritter(), emailConfirmationCheckBox.Checked ? new EmailInvoiceSender() : null }); DatabaseMethods.InsertClient(client); _mainForm.StartThreadQuantityUpdate(); Dispose(); } } }