Csharp 将FileStream的特定部分作为字节数组读取

您不应该手动设置位置.这条小溪无论如何都会向前推进.

您确实有另一个问题:您需要一个读取循环，因为缓冲区可能没有填满.读取循环将如下所示

    int bytesRead
    while ((bytesRead = await inputStream.ReadAsync(buffer, startPosition, buffer.Length) > 0)
    {
        startPosition += bytesRead;
        if (startPosition == buffer.Length)
            break;
    }

或者你可以用ReadAtLeastAsync

var bytesRead = await inputStream.ReadAtLeastAsync(buffer, buffer.Length, throwOnEndOfStream: false);

话虽如此，我建议你改用新的异步迭代器功能，这意味着你可以在这上面做await foreach分.

您还可以返回Memory<byte>，这在返回最后一个部分块时效率更高，否则必须将其复制到新的数组中.

public async IAsyncEnumerable<Memory<byte>> GetStreamChunksAsync(Stream inputStream, int numberOfChunks)
{
    if (numberOfChunks <= 0)
    {
        throw new ArgumentOutOfRangeException(nameof(numberOfChunks), numberOfChunks, "Invalid numberOfChunks or currentChunk values");
    }

    int bufferSize = (int)Math.Ceiling((double)inputStream.Length / numberOfChunks);

    while (true)
    {
        byte[] buffer = new byte[bufferSize];
        var bytesRead = await inputStream.ReadAtLeastAsync(buffer, buffer.Length, throwOnEndOfStream: false);
        if (bytesRead > 0)
            yield return buffer.AsMemory(0, bytesRead);
        if (bytesRead < buffer.Length)
            break;
    }
}

然后像这样使用它

await using var fs = File.Open("SomeFile");
await foreach (var chunk in GetStreamChunksAsync(fs, 10)
{
    // do stuff with chunk
}