How to trim IP Address to get the first 3 parts of it?

Question

I need to trim a given IP Address to get the first 3 parts of it

Example:

"192.168.1.20" ➨ "192.168.1."
"29.6.60.241" ➨ "29.6.60."

Answer 1

String result = input.Substring(0, input.LastIndexOf("."));

Answer 2

Using String.LastIndexOf(), it should be easy.

EDIT
Using that method you can locate the last '.'. Then you need a substring up to and (apparently) incuding that '.'. Something like:

string shortened = longIP.Substring(0,longIP.LastIndexOf(".")+1);