public Task <Response <Payment> > CancelAsync(CancelPaymentRequest request) { if (request == null) { throw new ArgumentNullException(nameof(request)); } if (string.IsNullOrWhiteSpace(request.Id)) { throw new ArgumentException("Value is null, empty or whitespace.", nameof(request.Id)); } return(PostAsync <Response <Payment> >( $"payments/{request.Id}/actions/cancel", new { payments = request } )); }