title: C#7 tuple & async
body: <p>Old format:  </p>
  
  <pre><code>private async Task&lt;Tuple&lt;SomeArray[], AnotherArray[], decimal&gt;&gt;         
  GetInvoiceDetailAsync(InvoiceHead invoiceHead) { ... }
  </code></pre>
  
  <p>How can you do that in C#7 with new tuples format?</p>