>I had find some Class in the File Download Area at this Site
>Unveralthread Had been complied which other can not read the source code of that!
>
>And My question is how can I did that with my custom Class
>

You can remove the source code from a .VCX by clearing the Method field from the class after compiling it. Make certain to keep a copy with the Method field intact, or you'll not be able to change the class once this is done.

Unless there is a very strong reason to remove the code from the .VCX, I'd recommend against doing so, but that's a decision you'd have to make for yourself. It makes maintenance that much more difficult for very little gain - the coe cn always be extracted after the fact using a tool like REFOX, so the technique will not defeat a dedicated hacker from pulling out the source.