private async Task Initialise()
{
_voucherService = new VoucherService();
_voucherResponse = await _voucherService.GetVouchers();
var vouchersList = new List <string> {
"Select Voucher"
};
vouchersList.AddRange(_voucherResponse.Select(x => x.Description).ToList());
var spnVoucher = FindViewById <Spinner>(Resource.Id.spnVoucher);
spnVoucher.ItemSelected += Voucher_OnSelected;
var voucherAdapter = new ArrayAdapter <string>(this, Android.Resource.Layout.SimpleSpinnerItem, vouchersList);
voucherAdapter.SetDropDownViewResource(Android.Resource.Layout.SimpleSpinnerDropDownItem);
spnVoucher.Adapter = voucherAdapter;
}