(Managed) DirectX 9.0x is the perfect example on how not to handle version numbering.
First, there is a “global” version problem which Jeff Atwood describes here. They are all 9.0c! Only the release date changes. So, you have plenty of 9.0c versions out there. Perhaps unmanaged libraries are all the same but managed wrappers certainly aren’t.
And here we come to the most complicated and chaotic versions numbering ever. It is a true obfuscation masterpiece. Fortunately, ZMan unveils the mystery in this post.
The bottom line is: avoid such versioning. And if you need to know which managed DirectX version is installed on your computer make sure you check ZMan’s post.