private void btnAdd_Click(object sender, EventArgs e)
        {
            decimal amount = 0;

            Decimal.TryParse(txtAmount.Text, out amount);

            placements_movements movement = new placements_movements()
            {
                account       = ((countables_accounts)cbAccount.SelectedItem).id,
                movement_type = cbMovementType.Text,
                amount        = amount
            };

            String errors = validateMovement(movement);

            if (errors.Length > 0)
            {
                MessageBox.Show(
                    errors,
                    "Error",
                    MessageBoxButtons.OK,
                    MessageBoxIcon.Error
                    );
            }
            else
            {
                movements.Add(movement);
                fillMovements(null);
                cleanMovementsFields();
            }
        }
        private String validateMovement(placements_movements movement)
        {
            StringBuilder sb = new StringBuilder();

            if (movement.amount <= 0)
            {
                sb.Append("- El monto introducido debe ser mayor a 0\n");
            }

            bool alreadyMovement = movements.Count(em => em.account == movement.account) > 0;

            if (alreadyMovement)
            {
                sb.Append("- Ya existe un movimiento con esta cuenta\n");
            }

            return(sb.ToString());
        }