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
void Regexes(string input)
{
var regex = new Regex("[A"); // Noncompliant
var match = Regex.Match(input, "[A"); // Noncompliant
var negativeLookahead = new Regex("a(?!b)", RegexOptions.NonBacktracking); // Noncompliant
var negativeLookbehind = new Regex("(?<!a)b", RegexOptions.NonBacktracking); // Noncompliant
}
Compliant solution
void Regexes(string input)
{
var regex = new Regex("[A-Z]");
var match = Regex.Match(input, "[A-Z]");
var negativeLookahead = new Regex("a(?!b)");
var negativeLookbehind = new Regex("(?<!a)b");
}
Resources
Documentation
