UWP 打开、保存文件示例

保存文件：

private async void RecDataSaveBtn(object sender, RoutedEventArgs e)
{
    string writingData = recvTbx.Text;
    FileSavePicker fp = new FileSavePicker();
    var filedb = new[] { ".txt"};
    fp.FileTypeChoices.Add("DB", filedb);
    fp.SuggestedFileName = "savedata" + DateTime.Now.Day + "-" + DateTime.Now.Month + "-" + DateTime.Now.Year;
    StorageFile sf = await fp.PickSaveFileAsync();
    if (sf != null)
    {
        using (StorageStreamTransaction transaction = await sf.OpenTransactedWriteAsync())
        {
            using (DataWriter dataWriter = new DataWriter(transaction.Stream))
            {
                dataWriter.WriteString(writingData);
                transaction.Stream.Size = await dataWriter.StoreAsync();
                await transaction.CommitAsync();
            }
        }
    }
}

打开文件：

private async void OpenFileBtn(object sender, RoutedEventArgs e)
{
    FileOpenPicker fop = new FileOpenPicker();
    fop.FileTypeFilter.Add(".txt");
    fop.FileTypeFilter.Add(".dat");

    StorageFile sf=await fop.PickSingleFileAsync();
    if (sf != null)
    {
        using (IRandomAccessStream readStream = await sf.OpenAsync(FileAccessMode.Read))
        {
            using (DataReader dataReader = new DataReader(readStream))
            {
                UInt64 size = readStream.Size;
                if (size <= UInt32.MaxValue)
                {
                    UInt32 numBytesLoaded = await dataReader.LoadAsync((UInt32)size);
                    string fileContent = dataReader.ReadString(numBytesLoaded);
                    sendTbx.Text = fileContent;
                }
            }
        }
    }
}