Api.Create

var invoice = Api.Create(new Invoice
            {
                Contact = new Contact { Name = "ABC Limited" },
                Type = InvoiceType.AccountsReceivable,
                LineItems = new List<LineItem>
                {
                    new LineItem
                    {
                        AccountCode = "200",
                        Description = "Good value item",
                        UnitAmount = 25.6m,
                        Quantity = 1m
                    },
                    new LineItem
                    {
                        AccountCode = "200",
                        Description = "Another good value item",
                        UnitAmount = 125.65m,
                        Quantity = 5m
                    }
                }
            });