Match Characters after last dot in string

Question

I have a string and I want to get the words after the last dot . in the string.

Example:

string input = "XimEngine.DynamicGui.PickKind.DropDown";

Result:

DropDown

`string result = input.SubString(input.LastIndexOf('.') + 1);` — Dmitry Bychenko, Aug 01 '19 at 12:39

Dmitry Bychenko · Answer 1 · 2023-08-19T22:33:48.743

7

There's no need in Regex, let's find out the last . and get Substring:

 string result = input.Substring(input.LastIndexOf('.') + 1);

If input doesn't have . the entire input will be returned.

Edit: Same code rewritten with a help of range:

string result = input[(input.LastIndexOf('.') + 1)..];

Finally, if you insist on regular expression, you can put it as

string result = Regex.Match(input, "[^.]*$", RegexOptions.RightToLeft).Value;

We match zero or more symbols which are not dot . starting from the end of the string (from the right).

edited Aug 19 '23 at 22:33

answered Aug 01 '19 at 12:39

Dmitry Bychenko

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This is written with thinking about performance. It will work faster than input.Split('.').Last(); – Sergey Kulgan Aug 31 '21 at 13:37
This should have been the accepted answer. – AFract Aug 19 '23 at 22:31

score 4 · Accepted Answer · answered Aug 01 '19 at 12:30

4

Not a RegEx answer, but you could do:

var result = input.Split('.').Last();

answered Aug 01 '19 at 12:30

pappbence96

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score 0 · Answer 3 · answered Aug 01 '19 at 13:54

In Regex you can tell the parser to work from the end of the string/buffer by specifying the option RightToLeft.

By using that we can just specify a forward pattern to find a period (\.) and then capture (using ( )) our text we are interested into group 1 ((\w+)).

var str = "XimEngine.DynamicGui.PickKind.DropDown";
Console.WriteLine(Regex.Match(str, 
                              @"\.(\w+)", 
                              RegexOptions.RightToLeft).Groups[1].Value);

Outputs to console:

DropDown

By working from the other end of the string means we don't have to deal with anything at the beginning of the string to where we need to extract text.

Match Characters after last dot in string

3 Answers3