XML Serializable "if"

I have created an xml file for a system with trophies and I would like a script (if) you were in control a certain thing written in the xml file as:
hello </ test>
I wish that the script in c # scrutiny as to whether there was evidence in the category really wrote hello, otherwise something would happen, how can I do?

See the documentation for XMLSerializer. The XMLSerializer serializes the XML file into a class structure, so it would be something like

if(XMLRoot.test != null){
 // do things here

Your class might not be named XMLRoot, though.