Download an object

using Amazon;
using Amazon.S3;
using Amazon.S3.Model;
using Amazon.S3.Util;

AmazonS3Config S3Config = new AmazonS3Config
{
  ServiceURL = "http://system.example.com"
};

string accessKeyId = "00000000000000";
string secretAccessKey = "000000000000000000000000000000";

AmazonS3Client client = new AmazonS3Client(accessKeyId , secretAccessKey ,S3Config);

// create a bucket
String bucketName = "testbucket";
PutBucketRequest request = new PutBucketRequest();
request.BucketName = bucketName;
client.PutBucket(request);

// create object request object
GetObjectRequest requestDownload = new GetObjectRequest
{ 
  BucketName = bucketName, 
  Key = "test"
};

// download physical file
using (GetObjectResponse response = client.GetObject(requestDownload))
{
  string dest = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop),
keyName);
  if (!File.Exists(dest))
  {
    response.WriteResponseStreamToFile(dest);
  }
}