Maybe:
const string EIDPattern = @"^(?<group1>[A-Za-z0-9]{4})(?:[/\s])(?<group2>[A-Za-z0-9]{5})(?:[/\s])(?<group3>[A-Za-z0-9]{2})$"
The
Input string can have space or other symbols also.
is not directly translatable to a valid regular expression statement, though.
You should have a look at
Expresso[
^].
Cheers.