Well... Except for sections and having spaces between the key, the = sign and the value, it's pretty much the same.
EDIT:
Run this regex for strings.
Then run this regex for more strings:
This one for boolean:
Floats:
And integers:
I put all regexes in " quotes and escaped the " quote character within. I didn't use regex with C# so far so I'm not sure if you use a string for it or if there is an integrated regex class (i.e. /(\S+) = (\d+\.\d+)/)
You will have to do some afterprocessing for the extensions though:
"(\S+?) = \[((?:.|\n)*)\]"
This will give a string with \n , ' and " characters which you will have to filter.
And keep in mind that this doesn't support comments with " and ' characters. In fact, comments should be avoided in the ini file.