c# Leave last 3 letters in a string

Question

How to remove letters from the string and leave just 3 last chars

Input:

foobar

Output:

bar

I tried:

string.Concat("foobar".Reverse().Skip(3).Reverse());

But that removes last 3 lines not keeps them

This is a duplicate of following: https://stackoverflow.com/questions/35691375/get-last-3-characters-of-string — Tejas Vaishnav, Mar 05 '20 at 12:40
@stickybit i think yes, this question should be marked as duplicate — Tejas Vaishnav, Mar 05 '20 at 12:41
Oh my, please *don't* take the last N chars of a string by creating at least 3 copies of the string by using Linq's Reverse() twice...That's just not a good way to do something better served by `string.Substring()`. — Matthew Watson, Mar 05 '20 at 12:42
@stickybit That question has been closed, and is not visible to lower-rep users — canton7, Mar 05 '20 at 12:44

Dmitry Bychenko · Answer 1 · 2020-03-05T12:43:11.057

8

Well, you can try Substring: if source is long enough we get Substring otherwise leave source intact:

 string source = ...

 string result = source.Length > 3 
   ? source.Substring(source.Length - 3) 
   : source;

Or even

 string result = source.Substring(Math.Max(0, source.Length - 3));

edited Mar 05 '20 at 12:43

answered Mar 05 '20 at 12:39

Dmitry Bychenko

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that works aswell thanks! – John Bielowski Mar 05 '20 at 12:41

canton7 · Answer 2 · 2020-03-05T12:52:15.090

7

Since C# 8, you can also use range syntax:

string result = source.Length > 3 ? source[^3..] : source;

or:

string result = source[^Math.Min(3, source.Length)..];

[^3..] is a range which means "start 3 elements from the end, and keep going until the end".

edited Mar 05 '20 at 12:52

answered Mar 05 '20 at 12:42

canton7

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I love this state of the art code (ranges) ;) – Dmitry Bychenko Mar 05 '20 at 12:44
Out of interest, I looked at the IL generated for this, and it does actually translate it into a call to `string.Substring()` so this is pretty optimal. – Matthew Watson Mar 05 '20 at 12:52
Yeah, it's got special support for arrays and strings, and it fakes indexers which take a range if the type has a suitable `Slice` method, and a `Length` or `Count` property – canton7 Mar 05 '20 at 12:56

Pavel Anikhouski · Answer 3 · 2020-03-05T12:48:33.627

3

There is a one line solution as well. Just check whether source string has enough length to get last 3 characters using Substring or leave string as is. Math.Max function will return a correct index

var str = "foobar";
var result = str.Substring(Math.Max(0, str.Length - 3));

edited Mar 05 '20 at 12:48

answered Mar 05 '20 at 12:42

Pavel Anikhouski

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c# Leave last 3 letters in a string

3 Answers3