How to add x509 (keyinfo)?

Hi!

I had a look over this project and the examples listed and I have a query. How to add a valid X509 public key and issuer in the signed xml?

I can see I can only call sig.AddX509Data(), however the result element is empty:

...
<ds:KeyInfo>
<ds:X509Data/>
</ds:KeyInfo>
...

Thanks!