Why is this an issue?
Regular expressions have their own syntax that is
understood by regular expression engines. Those engines will throw an exception at runtime if they are given a regular expression that does not
conform to that syntax.
To avoid syntax errors, special characters should be escaped with backslashes when they
are intended to be matched literally and references to capturing groups should use the correctly spelled name or number of the group.
Negative lookaround
groups cannot be combined with RegexOptions.NonBacktracking. Such
combination would throw an exception during runtime.
How to fix it
Code examples
Noncompliant code example
Sub Regexes(Input As String)
Dim Rx As New Regex("[A") ' Noncompliant: unmatched "["
Dim Match = Regex.Match(Input, "[A") ' Noncompliant
Dim NegativeLookahead As New Regex("a(?!b)", RegexOptions.NonBacktracking) ' Noncompliant: negative lookahead without backtracking
Dim NegativeLookbehind As New Regex("(?<!a)b", RegexOptions.NonBacktracking) ' Noncompliant: negative lookbehind without backtracking
End Sub
Compliant solution
Sub Regexes(Input As String)
Dim Rx As New Regex("[A-Z]")
Dim Match = Regex.Match(Input, "[A-Z]")
Dim NegativeLookahead As New Regex("a(?!b)")
Dim NegativeLookbehind As New Regex("(?<!a)b")
End Sub
Resources
Documentation
