private void SalesForm_Load(object sender, EventArgs e)
        {
            categoryComboBox.DataSource = _salesManager.CategoryComboLoad();
            categoryComboBox.Text       = "-Select-";

            customerComboBox.DataSource = _salesManager.CustomerComboLoad();
            customerComboBox.Text       = "-Select-";

            productComboBox.DataSource = _salesManager.ProductComboLoad();
            productComboBox.Text       = "-Select-";

            salesCodeTextBox.Text = _salesManager.SalesCode(sales.Code);
        }
        private void SalesForm_Load(object sender, EventArgs e)
        {
            try
            {
                _customers = _salesManager.CustomerComboLoad();
                customerComboBox.DataSource = _customers;
                customerComboBox.Text       = "-Select-";

                categoryComboBox.DataSource = _salesManager.CategoryComboLoad();
                categoryComboBox.Text       = "-Select-";

                productComboBox.Enabled = false;
                productComboBox.Text    = "-Select-";

                salesCodeTextBox.Text = _salesManager.SalesCode(_sales.Code);
            }
            catch (Exception error)
            {
                ExceptionMessage(error);
            }
        }