Evaluating XPath Expresssions

XPath Result of XPath Evaluation
string(/FitnessCenter/Member[1]/MembershipFee) + 1 Error!
data(/FitnessCenter/Member[1]/MembershipFee) + 1
341
data(340) + 1
341

The XML Document

<FitnessCenter>
        <Member id="1" level="platinum">
                <Name>Jeff</Name>
                <Phone type="home">555-1234</Phone>
                <Phone type="work">555-4321</Phone>
                <FavoriteColor>lightgrey</FavoriteColor>
                <MembershipFee>340</MembershipFee>
        </Member>
        <Member id="2" level="gold">
                <Name>David</Name>
                <Phone type="home">383-1234</Phone>
                <Phone type="work">383-4321</Phone>
                <FavoriteColor>lightblue</FavoriteColor>
                <MembershipFee>-500</MembershipFee>
        </Member>
        <Member id="3" level="platinum">
                <Name>Roger</Name>
                <Phone type="home">888-1234</Phone>
                <Phone type="work">888-4321</Phone>
                <FavoriteColor>lightyellow</FavoriteColor>
                <MembershipFee>340</MembershipFee>
        </Member>
</FitnessCenter>