This is an area where PowerShell shines. If you don’t already have it, install it. It’s preinstalled with Windows 7.
Running this command line:
[System.Reflection.Assembly]::LoadFrom("C:\full\path\to\YourDllName.dll").GetName().Version
outputs this:
Major Minor Build Revision
----- ----- ----- --------
3 0 8 0
Note that LoadFrom returns an assembly object, so you can do pretty much anything you like. No need to write a program.