Question

I need help extracting the value of a wildcard from a Regular Expressions match. For example:

Regex: “I like *”

Input: “I like chocolate”

I would like to be able to extract the string “chocolate” from the Regex match (or whatever else is there). If possible, I also want to be able to retrieve several wildcard values from a single wildcard match. For example:

Regex: “I play the * and the *”

Input: “I play the guitar and the bass”

I want to be able to extract both “guitar” and “bass”. Is there a way to do it?

Answer 1

In general regex utilize the concepts of groups. Groups are indicated by parenthesis.

So I like
Would be I like (.) . = All character * meaning as many or none of the preceding character

Sub Main()
    Dim s As String = "I Like hats"
    Dim rxstr As String = "I Like(.*)"
    Dim m As Match = Regex.Match(s, rxstr)
    Console.WriteLine(m.Groups(1))

End Sub

The above code will work for and string that has I Like and will print out all characters after including the ‘ ‘ as . matches even white space.

Your second case is more interesting because the first rx will match the entire end of the string you need something more restrictive.

I Like (\w+) and (\w+) : this will match I Like then a space and one or more word characters and then an and a space and one or more word characters

Sub Main()

    Dim s2 As String = "I Like hats and dogs"
    Dim rxstr2 As String = "I Like (\w+) and (\w+)"
    Dim m As Match = Regex.Match(s2, rxstr2)
    Console.WriteLine("{0} : {1}", m.Groups(1), m.Groups(2))
End Sub

For a more complete treatment of regex take a look at this site which has a great tutorial.