title: AWS SDK: Equivalent S3FileInfo methods for .net standard
body: <p>I'm working on upgrading our software to target .NET Standard.  I note that the AWS SDK does not support the AWS.S3.IO library, and therefore the <code>S3FileInfo</code> code we used previously needs to be updated.</p>
  
  <p>One that jumps out is the <code>Length</code> and <code>Exists</code> methods.  These used to do a HEAD request to S3 to determine what was required.  I can't see an equivalent right now - and it looks as though I'll have to do a <code>GetObjectRequest</code> instead, which is a full GET request.</p>
  
  <p>Is this correct, or is there a way to perform a HEAD operation to check for existence and length in the .NET Standard AWS SDK?</p>