用C＃写入txt文件

Question

I write to file data in this way.

I call out this function many times.

String ResultString = "data";
byte[] fileBytes = System.Text.Encoding.UTF8.GetBytes(ResultString);

StorageFolder local = Windows.Storage.ApplicationData.Current.LocalFolder;
StorageFolder dataFolder = await local.CreateFolderAsync("DataFolder", CreationCollisionOption.OpenIfExists);
StorageFile file = await dataFolder.CreateFileAsync("Data.txt", CreationCollisionOption.OpenIfExists);

using (var s = await file.OpenStreamForWriteAsync())
{
    s.Seek(0, SeekOrigin.End);
    s.Write(fileBytes, 0, fileBytes.Length);
}

The compiler skips StorageFile. Why dataFolder and local have the values NULL??

Answer 1

Try using async and await as it needs to be asynchronous.

 public static async Task<string> WriteFie()
    {
      string message = "abc";
      StorageFolder local =  Windows.Storage.ApplicationData.Current.LocalFolder;
      StorageFolder dataFolder = await local.CreateFolderAsync("DataFolder", CreationCollisionOption.OpenIfExists);
      StorageFile file = await dataFolder.CreateFileAsync("Data.txt", CreationCollisionOption.OpenIfExists);
      await FileIO.WriteTextAsync(file, message);
    }