Information
The topic you requested is included in another documentation set. For convenience, it's displayed below. Choose Switch to see the topic in its original location.

Alternation Constructs 

The following table lists special characters that modify a regular expression to allow either/or matching.

Alternation construct Definition

|

Matches any one of the terms separated by the | (vertical bar) character; for example, cat|dog|tiger. The leftmost successful match wins.

(?(expression)yes|no)

Matches the "yes" part if the expression matches at this point; otherwise, matches the "no" part. The "no" part can be omitted. The expression can be any valid subexpression, but it is turned into a zero-width assertion, so this syntax is equivalent to (?(?=expression)yes|no). Note that if the expression is the name of a named group or a capturing group number, the alternation construct is interpreted as a capture test (described in the next row of this table). To avoid confusion in these cases, you can spell out the inside (?=expression) explicitly.

(?(name)yes|no)

Matches the "yes" part if the named capture string has a match; otherwise, matches the "no" part. The "no" part can be omitted. If the given name does not correspond to the name or number of a capturing group used in this expression, the alternation construct is interpreted as an expression test (described in the preceding row of this table).

Was this page helpful?
(1500 characters remaining)
Thank you for your feedback

Community Additions

Show:
© 2014 Microsoft