so my .wxi file has these:

<?define MajorVersion="2" ?>
<?define MinorVersion="0" ?>
<?define BuildVersion="1" ?>

<?define PreRelease="a" ?>
<?define BuildMeta="" ?>

and I'd like to set the sementic version string depending if the PreRelease or BuildMeta strings are set. is this possible? The below doesn't work but i'd like to do something like this.

  <?if $(var.PreRelease.Length) -gt 0 ?>
     <?define SemVer = "$(var.MajorVersion).$(var.MinorVersion).$(var.BuildVersion)-$(var.PreRelease)"?>
     <?if $(var.BuildMeta) ?>
        <?if $(var.BuildMeta.Length) -gt 0 ?>
           <?define SemVer = "$(var.MajorVersion).$(var.MinorVersion).$(var.BuildVersion)-$(var.PreRelease)+$(var.BuildMeta)"?>
        <?endif?>
     <?endif?>
  <?endif?>