Get Index of a string from list of string

Question

I am trying to get values from a list. In the result I need the index of the value in the resulting list also. I dont have any idea how to get it. Can someone get me some ideas. Following is the code which i use.

        List<string> Lst1 = new List<string>();
        Lst1.Add("a");
        Lst1.Add("ab");
        Lst1.Add("c");
        Lst1.Add("d");

        List<string> result = Lst1.Select(x => x.Substring(0, 1)).ToList();

So you need index and value both in the result right ? IF that's the case you need the result as Dictionary — Mahesh
– Mahesh, Commented Jan 13, 2015 at 7:25
@CoderofCode: Not necessarily; an anonymous type might suffice as well. Depends on what they want to do with it. — Joey
– Joey, Commented Jan 13, 2015 at 7:26
Unfortunately it's not clear how you want to incorporate the original list index for the string in your result. Please edit the question so that it's clear what you're asking. — Peter Duniho
– Peter Duniho, Commented Jan 13, 2015 at 7:36

poke · Accepted Answer · 2015-01-13 07:27:42Z

4

Enumerable.Select has an overload that gives the index too, so you can just use that. Note that you cannot store both the string and the index in a List<string>, so you maybe need a List<Tuple<string, int>> instead. Also note, that in a list, each element already has an index, so you don’t really need this anyway.

List<Tuple<string, int>> result = Lst1.Select(
        (x, i) => new Tuple<string, int>(x.Substring(0, 1), i)).ToList();

answered Jan 13, 2015 at 7:27

poke

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2 Comments

Joey Over a year ago

@HamletHakobyan: That'd be Tuple.Create, I guess.

Peter Duniho Over a year ago

@HamletHakobyan: type inference doesn't work for constructors. But, that's why Microsoft provided the Tuple.Create() methods. So Tuple.Create(x.Substring(0, 1), i) works (and IMHO is preferable to specifying the type parameters explicitly).

Rahul Singh · Accepted Answer · 2015-01-13 07:32:27Z

1

You can use second overload of Enumerable.Select:-

 var result = Lst1.Select((v, i) => new { Value = v, Index = i });

Working Fiddle Demo.

edited Jan 13, 2015 at 7:32

answered Jan 13, 2015 at 7:26

Rahul Singh

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