Use regex inside Array.indexof in c#.net to find the index of element

Question

There is a list which adds the string at runtime. The string in the list can be like

List<string> myList=new List<string>();
  0    7- 9
  1    3 - 6
  2    1 -3
  3    10-12

Here the string contain in list does not have same pattern. Suppose I want to find the index of 3 - 6. So I have use an expression

3\s*\-\s*6

Now how to use it in Array.Indexof method so that I can get index of this element from mylist.

List<string> myList = new List(); should be List<string> myList = new List<string>(); shouldn't it? And why Regex? Why not simply use .Find() or .Contains()? — Tim
– Tim, Commented Sep 12, 2013 at 7:43
.contains will not work because in advance I dont know what would be the pattern of string in a list. — Proneet
– Proneet, Commented Sep 12, 2013 at 8:51

dcastro · Accepted Answer · 2013-09-12 09:33:19Z

2

Try

myList.FindIndex(s => new Regex(@"3\s*\-\s*6").Match(s).Success);

Edit: Working sample:

        List<string> myList = new List<string>
            {
                "7- 9",
                "3 - 6",
                "1 -3",
                "10-12"
            };
        int index = myList.FindIndex(s => new Regex(@"3\s*\-\s*6").Match(s).Success);


        Console.WriteLine(index); // 1

edited Sep 12, 2013 at 9:33

answered Sep 12, 2013 at 7:43

dcastro

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5 Comments

Proneet Over a year ago

its giving error as Expression cannot contain lambda expressions

dcastro Over a year ago

Hmm is that a compile-time error? Can you tell me more about the error?

dcastro Over a year ago

Also, forgot to put a @ before the regular expression, ive edited my answer.

dcastro Over a year ago

which line is throwing that error? the problem must be somewhere else in your code. I've tested this, and it works. Ive edited my answer and added a working sample.

Patrick McDonald Over a year ago

I believe its QuickWatch showing that error, the code is fine

No Idea For Name · Accepted Answer · 2013-09-12 07:42:15Z

0

you can do

str.Replace(" ", "");

and then you get rid of whitespace

and can just do

str.IndexOf("3-6");

answered Sep 12, 2013 at 7:42

No Idea For Name

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3 Comments

dcastro Over a year ago

Calling replace on every element might imply creating a whole new list of strings... and then doing a search.

No Idea For Name Over a year ago

@dcastro unless you insert it that way to the list. plus you don't have to create a new list. doing str.Replace(" ", "").IndexOf("3-6"); is possible...

dcastro Over a year ago

Correct me if I'm wrong, but I think he's searching for a string in a list, not a substring in a string (which is what str.Replace().IndexOf() does)...

Bibhu · Accepted Answer · 2013-09-12 09:03:58Z

0

Try this :

var match = Regex.Match(String.Join(String.Empty, myList.ToArray()), @"3\s*\-\s*6");

if (match.Success) {
    // match.Index to get the index
    // match.Value to get the value
}

edited Sep 12, 2013 at 9:03

answered Sep 12, 2013 at 7:42

Bibhu

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1 Comment

Proneet Over a year ago

@Bidhu I have list and not yourstring

MarcinJuraszek · Accepted Answer · 2013-09-12 09:14:34Z

0

You can do the same using LINQ:

var regex = new Regex(@"3\s*\-\s*6");
var index = myList.Select((x, i) => new { x, i })
                  .Where(x => regex.Match(x.x).Success)
                  .Select(x => x.i)
                  .First()

answered Sep 12, 2013 at 9:14

MarcinJuraszek

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