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