ganshani.com

Instantiate a FileInfo object with the full path as constructor arg. Then simply call FileInfo.Extension and you will get just the extension of the file.

FileInfo finfo = new FileInfo(strFileName);
Console.WriteLine(finfo.Extension);

Similarly, you can get more properties

Though this boils down to basics, these are most often missed out in projects and hence are performance issues.

http://ondotnet.com/pub/a/oreilly/dotnet/news/programmingCsharp_0801.html

The author has very beautifully touched on topics like:

1. Destructors
2. Dispose and Finalize
3. Value & Reference Types
4. Boxing
5. Structures
6. Virtual methods
7. and many more…

A must read for newbies…