How can I get the bytes of a GetObjectResponse from S3?

Here's the solution I found for anyone else who needs it:

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();
    }
}

I struggled to get the cleaner method offered by Alex to work (not sure what I'm missing), but I wanted to do it w/o the extra ReadStream method offered by Erica (although it worked)... here is what I wound up doing:

var s3Client = new AmazonS3Client(AccessKeyId, SecretKey, Amazon.RegionEndpoint.USEast1);
    using (s3Client)
    {
        MemoryStream ms = new MemoryStream();
        GetObjectRequest getObjectRequest = new GetObjectRequest();
        getObjectRequest.BucketName = BucketName;
        getObjectRequest.Key = awsFileKey;

        using (var getObjectResponse = s3Client.GetObject(getObjectRequest))
        {
            getObjectResponse.ResponseStream.CopyTo(ms);
        }
        var download = new FileContentResult(ms.ToArray(), "image/png"); //"application/pdf"
        download.FileDownloadName = ToFilePath;
        return download;
    }

Just another option:

Stream rs;    
using (IAmazonS3 client = Amazon.AWSClientFactory.CreateAmazonS3Client())
{
    GetObjectRequest getObjectRequest = new GetObjectRequest();
    getObjectRequest.BucketName = "mybucketname";
    getObjectRequest.Key = "mykey";

    using (var getObjectResponse = client.GetObject(getObjectRequest))
    {
              getObjectResponse.ResponseStream.CopyTo(rs);
    }
}