c# - HttpClient : limit response (downloaded file) size while using HttpResponseMessage. 内容.ReadAsStreamAsync()

Question

我正在寻找一种方法来控制下载文件的大小，同时使用以下代码:

    var client = new HttpClient();

    HttpResponseMessage resp = await client.GetAsync(mediaUri, HttpCompletionOption.ResponseHeadersRead);

    using (var fileStream = File.Create(outputPath))
    {
        using (var httpStream = await resp.Content.ReadAsStreamAsync())
        {
            httpStream.CopyTo(fileStream);
            fileStream.Flush();
        }
    }

如何防止下载大于预定义大小的文件？

编辑:

在下面的答案出现之前，我求助于用这个替换 CopyTo。我把它放在这里可能是为了根据以下答案对 ProgressMessageHandler 进行加权:

            using (var fileStream = File.Create(outputPath))
            {
                using (var httpStream = await resp.Content.ReadAsStreamAsync())
                {
                    // instead of httpStream.CopyToAsync(fileStream);
                    byte[] buffer = new byte[65536];
                    while (true)
                    {
                        int read = await httpStream.ReadAsync(buffer, 0, buffer.Length, ct);
                        if (read <= 0)
                            break;

                        // do the policing here

                        await fileStream.WriteAsync(buffer, 0, read);
                    }
                    fileStream.Flush();
                }
            }

Answer 1

尝试检查 the resp.Content.Headers.ContentLength property ，其中应包含文件的大小(以字节为单位)。