Decoding encodied Special Characters in XML (.Net / C#)

I am relatively new to using XML, so please bear with me.

I have an application which retrieves an XML file from a website. The XML file is the deserialised using a class created using XSD.

All works fine except for the conversion of encoded special characters (e.g. "&"), which are not being decoded when the XML is deserialised.

For example, the XML contains "This & That", and when it is deserialised, the text remains the same, and is not decoded to "This & That" as I'd expect.

I've dug around on Google, but I'm not sure where to go next.

Do I require some XmlAttribute somewhere to force the deserialiser to perform the conversion?  Or is it something I will have to attend to "manually"?

Any advise gratefully received.