private void UpdateSupplier(Supplier supplier)
        {
            try
            {
                var _supplier = Task.Run(async() => await Find(supplier.Id)).Result;
                _supplier.FirstName = supplier.FirstName ?? _supplier.FirstName;
                _supplier.LastName  = supplier.LastName ?? _supplier.LastName;
                _supplier.Telephone = supplier.Telephone ?? _supplier.Telephone;

                context.Entry <Supplier>(_supplier).State = Microsoft.EntityFrameworkCore.EntityState.Modified;
            }
            catch (NotSupportedException ex)
            {
                throw ex;
            }
            catch (ObjectDisposedException ex)
            {
                throw ex;
            }
            catch (InvalidOperationException ex)
            {
                throw ex;
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }
        private void UpdateCustomer(Customer customer)
        {
            try
            {
                var _customer = Task.Run(async() => await Find(customer.Id)).Result;
                _customer.FirstName = customer.FirstName ?? _customer.FirstName;
                _customer.LastName  = customer.LastName ?? _customer.LastName;
                _customer.Email     = customer.Email ?? _customer.Email;
                _customer.BirthDay  = customer.BirthDay ?? _customer.BirthDay;

                context.Entry <Customer>(_customer).State = Microsoft.EntityFrameworkCore.EntityState.Modified;
            }
            catch (NotSupportedException ex)
            {
                throw ex;
            }
            catch (ObjectDisposedException ex)
            {
                throw ex;
            }
            catch (InvalidOperationException ex)
            {
                throw ex;
            }
            catch (Exception ex)
            {
                throw ex;
            }
        }