It seems that I keep having to come up with a regular expression that validates and parses a version string. I often use this for customising TFS build workflows for extracting and using application version information.

The AssemblyVersionAttribute appears to have the following rules:

• Major version is required
• Minor version is optional and will default to 0 if not specified
• Minor version cannot be *
• Build and Revision versions are optional and may be *
• Revision number cannot be specified if the build number is *

The following is the regular expression that covers all these rules.

^
# Major version must exist
(?<VersionPart>\d+)
(
  # Minor only supports numbers
  \.(?<VersionPart>\d+)

  (\.
    (
      # Build can be *
      (?<VersionPart>\*)
      |
      # or a number
      (
        (?<VersionPart>\d+)

        # with optional Revision that may be * or numeric
        (\.(?<VersionPart>\*|\d+))?
      )
    )
  )? # Build.Revision is optional
)?$ # Minor.Build.Revision is optional

The following is the same expression without the comments and whitespace.

^(?<VersionPart>\d+)(\.(?<VersionPart>\d+)(\.((?<VersionPart>\*)|((?<VersionPart>\d+)(\.(?<VersionPart>\*|\d+))?)))?)?$

Enjoy.