private void UpdateButton_Click(object sender, EventArgs e)
        {
            const string errorMessage = "A supplier with this name doesn't exist.\n\nPlease enter a different name.";

            _connection = DB_Connect.connect();
            _connection.Open();

            if (IfSupplierExists(_connection, SNTextBox.Text))
            {
                var sqlQuery = @"UPDATE[Suppliers] SET[SupplierName] = '" + SNTextBox.Text + "', [SupplierAddress] = '" + SATextBox.Text + "' , [SupplierNumber] = '" + SNUTextBox.Text + "', [SupplierEmail] = '" + SETextBox.Text + "' WHERE[SupplierName] = '" + SNTextBox.Text + "'";
                ClearText();
                SNTextBox.Focus();
                _command = new SqlCommand(sqlQuery, _connection);
                _command.ExecuteNonQuery();
            }
            else
            {
                MessageBox.Show(errorMessage);
                SNTextBox.Clear();
                SNTextBox.Focus();
            }

            _connection.Close();
            LoadData();
        }
        private void AddButton_Click(object sender, EventArgs e)
        {
            const string errorMessage = "A supplier with this name already exists.\n\nPlease enter a different name.";

            _connection = DB_Connect.connect();
            _connection.Open();

            if (IfSupplierExists(_connection, SNTextBox.Text))
            {
                MessageBox.Show(errorMessage);
                SNTextBox.Clear();
                SNTextBox.Focus();
            }
            else
            {
                var sqlQuery = @"INSERT INTO[Suppliers] ([SupplierName], [SupplierAddress], [SupplierNumber], [SupplierEmail]) VALUES
                      ('" + SNTextBox.Text + "', '" + SATextBox.Text + "', '" + SNUTextBox.Text + "', '" + SETextBox.Text + "')";
                _command = new SqlCommand(sqlQuery, _connection);
                _command.ExecuteNonQuery();
                ClearText();
                SNTextBox.Focus();
            }

            _connection.Close();
            LoadData();
        }
 private void ClearText()
 {
     SETextBox.Clear();
     SATextBox.Clear();
     SNTextBox.Clear();
     SNUTextBox.Clear();
 }
 private void ClearText()
 {
     PCTextBox.Clear();
     PNTextBox.Clear();
     SNTextBox.Clear();
     SCTextBox.Clear();
     PriceTextBox.Clear();
     StockTextBox.Clear();
 }
        private void AddAccount()
        {
            string name    = FNTextBox.Text + " " + SNTextBox.Text;
            string x       = GenerateUN(FNTextBox.Text.ToLower(), DEPcb.Text.ToUpper());
            var    success = "You have successfully created an account!\n\nYour username is : " + x + "\nYour password is : default\n\nThis can be changed when you log in for the first time.";

            _connection = DB_Connect.connect();
            _connection.Open();

            var sqlQuery = @"INSERT INTO[Users] ([Name], [Department], [UserName], [Password], [AccessLevel]) VALUES
                      ('" + name + "', '" + DEPcb.Text + "', '" + x + "', '" + "default" + "', '" + ALcb.Text + "')";

            _command = new SqlCommand(sqlQuery, _connection);
            _command.ExecuteNonQuery();
            FNTextBox.Clear();
            SNTextBox.Clear();
            DEPcb.SelectedIndex = -1;
            ALcb.SelectedIndex  = -1;
            FNTextBox.Focus();
            MessageBox.Show(success);
            _connection.Close();
        }
        private void DeleteButton_Click(object sender, EventArgs e)
        {
            const string errorMessage = "This supplier does not exist!";

            _connection = DB_Connect.connect();

            if (IfSupplierExists(_connection, SNTextBox.Text))
            {
                _connection.Open();
                var sqlQuery = @"DELETE FROM[Suppliers] WHERE[SupplierName] = '" + SNTextBox.Text + "'";
                _command = new SqlCommand(sqlQuery, _connection);
                _command.ExecuteNonQuery();
                _connection.Close();
            }
            else
            {
                MessageBox.Show(errorMessage);
            }

            ClearText();
            SNTextBox.Focus();
            LoadData();
        }