UWP：异步读取文件到 byte[]

Question

我想将本地存储的文件读入字节数组。我怎么做？这是我的尝试：

StorageFolder folder = await StorageFolder.GetFolderFromPathAsync(filePath);
var file = await folder.GetFileAsync(filePath);
var buffer = await FileIO.ReadBufferAsync(file);
DataReader dataReader = Windows.Storage.Streams.DataReader.FromBuffer(buffer);
// doesn't work because ReadBytes wants a byte[] as parameter and also isn't asynchronous
byte[] result = dataReader.ReadBytes(buffer.Length);

Answer 1

我想到了三个概念 - 使用 FileStream 并修改您的方法：

第一个通过提供的缓冲区读取字节，尽管此方法需要 seekable 流：

FileOpenPicker picker = new FileOpenPicker();
picker.FileTypeFilter.Add(".txt");
using (Stream fileStr = await (await picker.PickSingleFileAsync()).OpenStreamForReadAsync())
{
    byte[] bytes = new byte[fileStr.Length];
    const int BUFFER_SIZE = 1024;
    byte[] buffer = new byte[BUFFER_SIZE];
    int position = 0;
    int bytesread = 0;
    while ((bytesread = await fileStr.ReadAsync(buffer, 0, BUFFER_SIZE)) > 0)
       for (int i = 0; i < bytesread; i++, position++)
           bytes[position] = buffer[i];
}

第二种方法是异步复制文件流到内存然后以数组形式获取：

using (MemoryStream memStream = new MemoryStream())
using (Stream fileStr = await (await picker.PickSingleFileAsync()).OpenStreamForReadAsync())
{
    await fileStr.CopyToAsync(memStream);
    byte[] bytes = memStream.ToArray();
}

你的方法几乎没有修改 - 通过内存流处理：

var buffer = await FileIO.ReadBufferAsync(file);
using (MemoryStream mstream = new MemoryStream())
{
     await buffer.AsStream().CopyToAsync(mstream);
     byte[] result = mstream.ToArray();
}

或者最好避免使用 byte[] 而是使用 IBuffer 或 MemoryStream.

Answer 2

        StorageFolder storageFolder = ApplicationData.Current.LocalFolder;
        StorageFile sampleFile = await storageFolder.GetFileAsync(FILE_NAME);

        byte[] result;
        using (Stream stream = await sampleFile.OpenStreamForReadAsync())
        {
            using (var memoryStream = new MemoryStream())
            {

                stream.CopyTo(memoryStream);
                result = memoryStream.ToArray();
            }
        }

Answer 3

我认为其他答案使事情不必要地复杂化。为此，有一个方便的扩展方法IBuffer.ToArray()。

只需这样做：

using System.Runtime.InteropServices.WindowsRuntime;
using Windows.Storage;
...
IStorageFile file;
IBuffer buffer = await FileIO.ReadBufferAsync(file);
byte[] bytes = buffer.ToArray();

UWP：异步读取文件到 byte[]

UWP: async read file into byte[]

c#

windows-phone

win-universal-app

windows-10-mobile