Check if a string is null or empty in XSLT

Question

How can I check if a value is null or empty with XSL?

For example, if categoryName is empty? I\'m using a when choosing construct.

For

Answer 1

How can I check if a value is null or empty with XSL?

For example, if categoryName is empty?

This is probably the simplest XPath expression (the one in accepted answer provides a test for the opposite, and would be longer, if negated):

not(string(categoryName))

Explanation:

The argument to the not() function above is false() exactly when there is no categoryName child ("null") of the context item, or the (single such) categoryName child has string value -- the empty string.

I'm using a when choosing construct.

For example:

In XSLT 2.0 use:

Here is a complete example:

When this transformation is applied on the following XML document:

X

the wanted, correct result is produced:

X

When applied on this XML document:

or on this:

or on this

Y

the correct result is produced:

Other

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Similarly, use this XSLT 1.0 transformation:

Do note: No conditionals are used at all. Learn more about the importance of avoiding conditional constructs in this nice Pluralsight course:

"Tactical Design Patterns in .NET: Control Flow"