Question

我有两种功能相同的方法：

private static async Task<IRandomAccessStream> _DownloadImage(string url)
{
    HttpClient http = new HttpClient();
    var httpStream = await http.GetStreamAsync(url);
    var memStream = new MemoryStream();
    await httpStream.CopyToAsync(memStream);
    memStream.Seek(0, SeekOrigin.Begin);
    return memStream.AsRandomAccessStream();
}

和

private static async Task<IRandomAccessStream> _DownloadImage2(string url)
{
    HttpClient http = new HttpClient();
    var httpStream = await http.GetStreamAsync(url);
    var stream = new InMemoryRandomAccessStream();
    await httpStream.CopyToAsync(stream.AsStreamForWrite());
    stream.Seek(0);
    return stream;
}

问题是，对于某些网址，第二个版本的长度为stream。这是一个错误还是我错过了什么？第一个版本为普通流提供图片而第二个版本为空的网址：http://icdn.lenta.ru/images/2014/09/17/10/20140917102331786/pic_ffa73ea27023b3e69b6cef4d068c0499.jpg

UPD：

我发现大小低于16384的文件存在风险。我在AsStreamForWrite文档中找到了这个16384值。 @Kiewic，也提出了一个解决方法。我仍然想知道为什么它不能正常工作。

UPD2： 在Connect。中创建了bug report。

Answer 1

当您将Stream保留在变量中时，它会起作用，请尝试：

// using System.Net.Http;

private static async Task<IRandomAccessStream> _DownloadImage2(string url)
{
    HttpClient http = new HttpClient();
    var httpStream = await http.GetStreamAsync(url);
    var stream = new InMemoryRandomAccessStream();

    Stream streamForWrite = stream.AsStreamForWrite();
    await httpStream.CopyToAsync(streamForWrite);

    stream.Seek(0);
    Debug.WriteLine("Length: " + streamForWrite.Length);
    Debug.WriteLine("Size: " + stream.Size);

    return stream;
}

InMemoryRandomAccessStream不正确（？）行为

1 个答案: