Using regular expressions to get a word in between two Key words

Question

It has been a while since I have used regular expressions and I'm hoping what I'm trying to do is possible. I have a program that sends automated response regarding a particular file and I'd like to grab the text between two words I know will never change. In this example those words are "regarding" and "sent"

Dim subject As String = "Information regarding John Doe sent."
Dim name As String = Regex.IsMatch(subject, "")

So in this case I'd like to be able to get just "John Doe". Every regexp I'm coming up with includes the words "regarding" and "sent". How can I use those words as the boundaries but not include them in the match?

Answer 1

Assuming "Information regarding " and "sent." never change, you can use a capturing group to get "John Doe":

^Information regarding (.+) sent.$

And you use it this way:

Dim regex As New Regex("^Information regarding (.+) sent.$")
Dim matches As MatchCollection = regex.Matches(subject)

Now, it should only match once, and you can get the group from the Groups property of the match:

For Each match As Match In matches  
  Dim groups As GroupCollection = match.Groups
  Console.WriteLine(groups.Item(1).Value) // prints John Doe
Next

Answer 2

Your regular expression should essentially look like this:

.*regarding (.+) sent.*

And the data you're looking for will be in the first capture variable ($1 in Perl).

Answer 3

While matching all the groups is a way of doing, I would use two non matching groups and one named froup so that it would only ever return the group that you wanted. This would give you the regex:

(?:regarding )(?<filename>.*)(?: sent)

this would give you the ability to call the filename from the groups for example

Dim rx As New Regex("(?:regarding )(?<filename>.*)(?: sent)", _
           RegexOptions.Compiled )
Dim text As String = "Information regarding John Doe sent."
Dim matches As MatchCollection = rx.Matches(text)
'The lazy way to get match, should print 'John Doe'
Console.WriteLine( matches[0].Groups.Item("filename").Value )

A good resource for Regex is found on the msdn site here