private bool IsUniqueCustomerId(int id)
 {
     CustomerContext context = new CustomerContext();
     if (context.Customer.Any(x => x.CustomerId == id))
         return false;
     return true;
 }
 public OrderDetailsForm(Customer selectedCustomer, CustomerContext context, Order editOrder = null)
 {
     _context = context;
     InitializeComponent();
     this.comboBoxClient.DataSource = _context.Customer.Local.ToBindingList();
     if (editOrder != null) // edit order
     {
         _order = editOrder;
         _updateMode = true;
         SetInitialData(editOrder);
     }
     else // add new order
     {
         _order = new Order();
         _updateMode = false;
         if (selectedCustomer != null)
             this.comboBoxClient.SelectedValue = selectedCustomer.CustomerId;
     }
     this.Shown += OrderDetailsForm_Shown;
 }