First split then join a subset of a string

Question

I have an input string as follows:

thumb_634735515600845357tchayat_november_200612.jpg

What I want to do is first split this string by _. And then take the resulting tokens at positions 1 to n and join them.

Specifically, with respect to my sample input, here is my desired output. As you can see, thumb_ has been removed from the front of the string:

634735515600845357tchayat_november_200612.jpg

I know how to do the split. But then how do I do the join step that follows? I do realize that I can use a for loop to do the join. But is there a better way? I can't use a sub-string approach to do the join step because I have data before thumb_.

Finally, note that the _ character that follows thumb is always the first instance of _.

score 12 · Accepted Answer · edited May 23 '17 at 10:29

12

Since the _ after the thumb is always the first instance then Substring should be perfectly viable in conjunction with IndexOf.

string newString = myString.Substring(myString.IndexOf("_") + 1);

This should take the substring starting at the character immediately following the first instance of the _ character.

If you wish to get the second index of _, here's what I recommend:

int first = myString.IndexOf("_");
int second = mystring.Substring(first).IndexOf("_");

See this answer by Jon Skeet to the question "Index of the nth occurrence of a string?" for support for this approach.

edited May 23 '17 at 10:29

Community

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answered Jun 14 '12 at 01:58

Joel Etherton

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Since C#8 and the introduction of Range Structs, the recommended format for the first line of code would now be myString[(myString.IndexOf("_") + 1)..] – Haighstrom Apr 11 '22 at 14:57

score 7 · Answer 2 · edited Jun 14 '12 at 02:07

7

If you don't like indexOf, but want Join instead:

String.Join("_",
   "thumb_634735515600845357tchayat_november_200612.jpg"
   .Split('_')
   .Skip(1)
   .ToArray())

edited Jun 14 '12 at 02:07

DarthVader

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answered Jun 14 '12 at 01:58

Alexei Levenkov

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+1: I like this if IndexOf is not available for some reason. It's a little "chattier" than the IndexOf solution, but a very good alternate. – Joel Etherton Jun 14 '12 at 02:00
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It will not add _ in result as 634735515600845357tchayatnovember200612.jpg – Niranjan Singh Jun 14 '12 at 02:03
actually you are right. that s the result for this and not reallyw hat i want – DarthVader Jun 14 '12 at 02:08

score 2 · Answer 3 · answered Jun 14 '12 at 02:01

2

After splitting and rearranging you can use Join method.

string new_value=String.Join("",your_array);

answered Jun 14 '12 at 02:01

Md Kamruzzaman Sarker

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Kirin Yao · Answer 4 · 2012-06-14T02:08:52.923

0

You can use String.Join, but actually, it still use a loop inside.

String.Join("_", "thumb_634735515600845357tchayat_november_200612.jpg".Split('_').Skip(1).ToArray());

edited Jun 14 '12 at 02:08

answered Jun 14 '12 at 02:03

Kirin Yao

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why do u have 1 and 3? what if u have more _? – DarthVader Jun 14 '12 at 02:10
@DarthVader Yes, you're right. Should use `Skip` instead. I'll edit my answer. – Kirin Yao Jun 14 '12 at 02:13
@DarthVader Do you mean there are more `_` before "thumb"? – Kirin Yao Jun 14 '12 at 02:17

score 0 · Answer 5 · edited Aug 10 '19 at 10:29

0

UserRoles are the list of strings:

string.Join(",", userRoles.ToArray());

edited Aug 10 '19 at 10:29

Prashant Pimpale

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answered Oct 06 '14 at 07:21

Mohamed.Abdo

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T.CK · Answer 6 · 2019-10-10T02:35:56.997

Original post was on Aug. 31, 2015. The only thing that I've changed is the markup syntax because the original was wrong.

The use of regular expressions can be very helpful.

using System.Text.RegularExpressions;

string itemName = "thumb_634735515600845357tchayat_november_200612.jpg";
itemName = Regex.Match(itemName, @"(?<=(_)).*$").Value;

The "(?<=(_))" looks behind the first "_". Think of it as a starting point. The ".*$" gets everything from the starting point to the end of the line. "$" marks the end of the line.

First split then join a subset of a string

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