Can I Use Vlfeat Library In C# Project?

you can most likely use vlfeat from c#, [but] you'd have to use p/invoke - if there's no c# image processing library that gives you what you need, it may be your only choice.

If the vlfeat c api is tricky to p/invoke, you could use a 'middle layer', ie, aggregate the transforms/functions you want into a 'c' dll and export a simpler interface for the benefit of calling via p/invoke from c# - so you end up with a 'stack' like I've shown below

c# - calls middle layer
using p/invoke
- - - - - - - - - - - - - -
middle layer - aggregate
of vlfeat functions into
useable business functions
in 'c' dll
- - - - - - - - - - - - - -
vlfeat api raw functions