Question

I need to obtain from a string version (of maximum 3 chars like sql varchar(3), the “next version” with the following simple rule:

if its last chars constitutes a number, increment it, if it always fits max 3 chars, else, leave it as is.

Say “Hi1” => “Hi2”, “H9” => “H10” but “xx9” will remain unchanged.

  Public Shared Function GetNextVersion(oldVersion As String) As String
    Dim newVersion As String = String.Empty
    If Regex.IsMatch(oldVersion, "?????") Then
      Return newVersion
    Else
      Return oldVersion
    End If
  End Function

Answer 1

This will be your regex, it will match anything with a gruop of letters followed by a group of numbers.

Public Dim regex As Regex = New Regex( _
      "^(?<prefix>.*?0*)(?<version>\d+)$", _
      RegexOptions.IgnoreCase _
        Or RegexOptions.CultureInvariant _
        Or RegexOptions.Compiled _
    )

It will contain two named capture groups, “prefix” which is the initial characters, and “version” which has your version.

Cast the version to an int, increment it, and return the new version number by concatenating the prefix and new version.

So, you’ll end up with something like this

Public versionRegex As Regex = New Regex( _
   "^(?<prefix>.*?0*)(?<version>\d+)$", _
   RegexOptions.IgnoreCase _
     Or RegexOptions.CultureInvariant _
     Or RegexOptions.Compiled _
 )

Public Shared Function GetNextVersion(oldVersion As String) As String
    Dim matches = versionRegex.Matches(oldVersion)
    If (matches.Count <= 0) Then
        Return oldVersion
    End If

    Dim match = matches(0)
    Dim prefix = match.Groups.Item("prefix").Value
    Dim version = CInt(match.Groups.Item("version").Value)

    Return String.Format("{0}{1}", prefix, version + 1)
End Function