如何使用response.WriteResponseStreamToFile将文件下载到downloads文件夹？ （Amazon S3，C＃）

Question

我在S3中存储了一些PDF，我试图建立一个可以下载它们的链接。这是我到目前为止的方法：

public virtual ActionResult DownloadPDF(string filename)
{
    string secretKey = this.UnitOfWork.ApplicationSettingRepository.GetOrCreateByName<string>("StorageProvider_AmazonS3_SecretKey");
    string accessKey = this.UnitOfWork.ApplicationSettingRepository.GetOrCreateByName<string>("StorageProvider_AmazonS3_AccessKey");
    var bucket = this.UnitOfWork.ApplicationSettingRepository.GetOrCreateByName<string>("StorageProvider_AmazonS3_BucketName");
    var serviceUrl = this.UnitOfWork.ApplicationSettingRepository.GetOrCreateByName<string>("StorageProvider_AmazonS3_ServiceUrl");

    AmazonS3Config config = new AmazonS3Config();
    config.ServiceURL = serviceUrl;

    var client = Amazon.AWSClientFactory.CreateAmazonS3Client(
            accessKey,
            secretKey,
            config
            );
    GetObjectRequest request = new GetObjectRequest();
    request.BucketName = bucket;

    request.Key = "userfiles/MSD IMAGES/ProductDocumentation/" + filename;
    GetObjectResponse response = client.GetObject(request);
    response.WriteResponseStreamToFile("\\Downloads\\" + filename);
}

我从本文档here获得了该方法，但我想下载要在浏览器中显示的下载，并转到标准下载文件夹。我之前创建了这个方法来下载csv文件：

var csv = new StringBuilder();
csv.AppendLine("col1,col2,col3");

var bytes = Encoding.UTF8.GetBytes(csv.ToString());

var response = new FileContentResult(bytes, "text/csv");
response.FileDownloadName = fileName;
return response;

我尝试用S3文件做同样的事情：

GetObjectResponse response = client.GetObject(request);
// response.WriteResponseStreamToFile("\\Downloads\\" + filename);
var bytes = Encoding.UTF8.GetBytes(response.ToString());
var download = new FileContentResult(bytes, "application/pdf");
download.FileDownloadName = filename;
return download;

它下载了一个文件，但pdf不起作用（无法加载）。如何下载从S3获得的文件？

Answer 1

您需要执行以下操作

int byteCount
byte[] buffer = new byte[2048]; // read in chunks of 2KB
Stream responseStream= Response.GetResponseStream();
Response.ContentType = "application/pdf";
Response.AddHeader("Content-Disposition", "attachment;filename=" + filename);

while ((byteCount = responseStream.Read(buffer, 0, buffer.Length)) > 0)
{
    Response.OutputStream.Write(buffer, 0, byteCount);    
}

Response.Flush();
Response.Close();
Response.End();

Answer 2

这是我提出的工作解决方案：

GetObjectResponse response = client.GetObject(request);
using (Stream responseStream = response.ResponseStream)
{
    var bytes = ReadStream(responseStream);
    var download = new FileContentResult(bytes, "application/pdf");
    download.FileDownloadName = filename;
    return download;
}

public static byte[] ReadStream(Stream responseStream)
{
    byte[] buffer = new byte[16 * 1024];
    using (MemoryStream ms = new MemoryStream())
    {
        int read;
        while ((read = responseStream.Read(buffer, 0, buffer.Length)) > 0)
        {
            ms.Write(buffer, 0, read);
        }
        return ms.ToArray();
    }
}