Get Second to last character position from string

Question

I have a dynamically formed string like - part1.abc.part2.abc.part3.abc

In this string I want to know position of second to last "." so that i can split string as part1.abc.part2.abc and part3.abc

let me know is there any direct method available to get this?

Answer 1

string str = "part1.abc.part2.abc.part3.abc";
int ix1 = str.LastIndexOf('.');
int ix2 = ix1 > 0 ? str.LastIndexOf('.', ix1 - 1) : -1;

There are always lovers of Regexes (and jQuery), so I'll give a Regex solution (for the jQuery solution you'll have to wait :-) ):

var match = Regex.Match(str, @"\.[^\.]*\.", RegexOptions.RightToLeft);
int ix = match.Success ? match.Index : -1;

(note that I'm an hater of Regexes, I'm giving it to you so that you can have enough rope to hang yourself if you so choose).

Be aware that I'm using the RegexOptions.RightToLeft option so that the Regex starts at the last character.

Answer 2

You can use the String.LastIndexOf('.') method to get the position of the last full-stop/period, then use that position in a second call to LastIndexOf('.') to get the last but one, e.g.:

string aString = "part1.abc.part2.abc.part3.abc";
int lastPos = aString.LastIndexOf('.');

int lastPosButOne = aString.LastIndexOf('.', lastPos - 1);

But I'd recommend using String.Split('.') which will give you an array of the string parts, then you can take the last but one, e.g.

string aString = "part1.abc.part2.abc.part3.abc";
string[] parts = aString.Split('.');

string lastPartButOne = parts[parts.Length - 1];