// 保存记账列表
public async void SaveToFile()
{
await StorageFileHelper.WriteAsync <List <Voucher> >(this._data, "Voucher.dat");
}
// 读取记账列表
public async Task <bool> LoadFromFile()
{
this._data = await StorageFileHelper.ReadAsync <List <Voucher> >("Voucher.dat");
return(this._data != null);
}