reduse size for any file

Please see my comment to the question. It's not clear what do you mean by "reduce" here, but you should understand that most files can be effectively compressed in smaller size in a lossless way:
http://en.wikipedia.org/wiki/Lossless_compression[^].

If could be, among many other algorithms, Deflate, GZip or ZIP. Please see:
http://msdn.microsoft.com/en-us/library/system.io.compression.aspx[^].

For working with ZIP, you can use #ziplib:
http://www.icsharpcode.net/opensource/sharpziplib/[^].

Another option is using SevenZipSharp, a .NET wrapper of the famous 7-Zip:
http://en.wikipedia.org/wiki/7-Zip[^],
http://sevenzipsharp.codeplex.com/[^].

Both ZIP libraries are open-source.

—SA