Introducing Microsoft® Office InfoPath™ 2003

Calculating Values with the Expression Box

An expression box is an unbound, read-only text box that displays the value of an XPath expression. The most common use of expression boxes is to display the result of mathematical operations on numeric field values, but you also use expression boxes to display text values, such as the full name of a person from firstName and lastName field values. As you learned in Chapter 3, XPath is a language for navigating the in-memory representation of XML documents—called the XML Document Object Model, or XML DOM—to select specific nodes and subnodes by name. If you specify a leaf node or an attribute name as the expression, XPath returns the value of the node or attribute to the expression box. XPath also offers ...