My Vim 7.3 runtime has a syntax/cs.vim
file (from 14-Aug-2009) that supports syntax folding for #region
. Syntax folding is nice; I'd advise against another foldmethod. I would contact the author of the syntax file and suggest the missing folding of functions as an enhancement; many other filetypes have this, and it seems to be common and helpful. (This can be made configurable for those who don't want one or the other.)
In the meantime, you can add the following to ~/.vim/after/syntax/cs.vim
to enable folding of any curly braces blocks:
syn region csFold start="{" end="}" transparent fold