Question

I’ll have to read a regex tutorial – so far I have a mental block in this area – right now I am just trying to match the following pattern:

ab234_12345_45678_afddsyyht788959

I am trying to extract the third (likely numeric) item surrounded by underscores (if the string has the wrong pattern, return invalid format, of course).

Something like:

Dim strOriginal As String = "ab234_12345_45678_afddsyyht788959"
Dim strFound As String
Try
    Dim matches As MatchCollection
    Dim regexStuff As New Regex("_.*?_")
    matches = regexStuff.Matches(strOriginal)
    strFound = matches.Item(0).Groups(2).Value.ToString
Catch
    strFound = "invalid"
End Try
MessageBox.Show(strFound)

The problem is with the pattern – I can’t figure out anything that works… (I have tried a few other patterns too)

Answer 1

Use this regex

[A-Za-z0-9]+_[A-Za-z0-9]+_([A-Za-z0-9]+)

Match the \1 group

If you want the third group to be numeric replace ([A-Za-z0-9]+) with (\d+)