You must have READ access to the object.

If READ access is granted to an anonymous user, an object can be retrieved without an authorization header. Providing a version-id for the object will fetch the specific version from S3 instead of the most recent one.

You should wrap the response you get from calling GetObject in a using clause. This ensures that all underlying IO resources allocated for the response are disposed once the response has been processed. This is one way to call GetObject:

CopyC#

using (GetObjectResponse response = s3Client.GetObject(request))
{
    ... Process the response:
    Get the Stream, get the content-length, write contents to disk, etc
}

This example shows how to get an object.

CopyGetObject sample

// Create a client
AmazonS3Client client = new AmazonS3Client();

// Create a GetObject request
GetObjectRequest request = new GetObjectRequest
{
    BucketName = "SampleBucket",
    Key = "Item1"
};

// Issue request and remember to dispose of the response
using (GetObjectResponse response = client.GetObject(request))
{
    using (StreamReader reader = new StreamReader(response.ResponseStream))
    {
        string contents = reader.ReadToEnd();
        Console.WriteLine("Object - " + response.Key);
        Console.WriteLine(" Version Id - " + response.VersionId);
        Console.WriteLine(" Contents - " + contents);
    }
}