How to check if a named capture group exists?

Question

In my regex the pattern is something like this:

@"Something\(\d+, ""(.+)""(, .{1,5}, \d+, (?<somename>\d+)?\),"

So I would like to know if <somename> exists. If it was a normal capture group, I could just check if the capture groups are greater than the number of groups without that/those capture group(s), but I don't have the option here.

Could anyone help me find a way round this? I don't need it to be efficient, it's just for a one-time program that's used for sorting, so I don't mind if it takes a bit to run. It's not going to be for public code.

Answer 1

According to the documentation:

If groupname is not the name of a capturing group in the collection, or if groupname is the name of a capturing group that has not been matched in the input string, the method returns a Group object whose Group.Success property is false and whose Group.Value property is String.Empty.

var regex = new Regex(@"Something\(\d+, ""(.+)""(, .{1,5}, \d+, (?<somename>\d+)?\),");
var match = regex.Match(input);
var group = match.Groups["somename"];
bool exists = group.Success;