Attach unencrypted tag data to encrypted file

I hope this is the right place for my question, since there's definitely more than one way to do it.

I have a file format (xml) that I compress and encrypt. The thing is now that I want to attach some basic unencrypted meta-data to my file for ease of access to certain parameters.

Is there a right way to do what I want to do, otherwise what are some best practices to keep in mind?

The approach that I'm thinking about now is to use Bouncy Castle in C# to encrypt my actual data while prepending my tag data to the front of the file.

e.g.

<metadata>
    //tag information about the file
</metadata>
<secretdata>
    //Grandma's secret recipe
</secretdata>

Encrypt secret data only

<metadata>
    //tag information about the file
</metadata>
^&RF&^Tb87tyfg76rfvhjb8
hnjikhuhik*&GHd65rh87yn
NNCV&^FVU^R75rft78b875t