Problem when creating a DataSet from a XSD file

I would like to create a DataSet object from a XSD file.

I wrote the following code:

DataSet myDS = new DataSet();
myDS.ReadXmlSchema(filepath);

when I run my App I get the following DataSet exception:

"DataSet doesn't support 'union' or 'list' as simpleType."

Do you know if it is an error I can get ride off
I tried to search on google but I didn't fond anything interesting at all...
The XSD file I tried to load is of course valid and I got it from "http://ns.hr-xml.org".

I can provide more informations, files, Exception details etc. if you need

Thank you in advance for your precious help.

Steph.