c# - 如何使用 Amazon S3 ResponseStream 返回 FileResult？

Question

使用 AWSSDK.S3 nuget 包，我试图返回一个从 S3 存储桶中检索到的文件。我的出发点是基于此 SO answer 中给出的示例.

示例 Controller 代码:

public FileResult GetFile(Guid id)
{
    // no using block as it will be disposed of by the File method
    var amazonResponse = _foo.GetAmazonResponseWrapper(_user, id);
    // set Response content-length header
    // set Response content-type header

    var bufferSize = 1024;
    var buffer = new byte[bufferSize];
    int bytesRead;

    while ((bytesRead = amazonResponse.ResponseStream.Read(buffer, 0, buffer.Length)) > 0 && Response.IsClientConnected)
    {
        Response.OutputStream.Write(buffer, 0, bytesRead);
        Response.OutputStream.Flush();
        buffer = new byte[bufferSize];
    }        

    // this will not work (can't read from this stream)
    return File(Response.OutputStream, "text/plain", "bar.txt");
}

如果我写入在 while 循环中创建和使用的 MemoryStream，我将得到一个文件，但不会有任何内容。

我发现获取文件内容的唯一方法是像这样在流上调用 .ToArray():

return File(memStream.ToArray(), "text/plain", "foo.txt");

有没有一种方法可以将文件实际流式传输到浏览器，而无需将其加载到网络服务器的内存中？

Answer 1

只是向前传递流

public FileResult GetFile(Guid id) {
    // no using block as it will be disposed of by the File method
    var amazonResponse = _foo.GetAmazonResponseWrapper(_user, id);
    return File(amazonResponse.ResponseStream, "text/plain", "bar.txt");
}

您已经证明可以从响应流中读取。然后只需传递响应流，File 结果将读取它并返回响应。