Search string in list using linq

Question

I had a list List<string> Rank

items in list Rank are

"FF"
"ABC"
"CC"
"FF"
"FF"

I want a linq query that return value if exist and its count, suppose If i search for "FF" then it should return

value: ff
count: 3

currently i am using this query to find the match

var match = Rank.FirstOrDefault(s => s.Contains("FF"));

and this query to group the same values and assign them count.

var f = Rank.GroupBy(x => x).Select(g => new { Value = g.Key, Count = g.Count() });

i tried this but it return me complete list, it look like where clause not

var f = Rank.GroupBy(x => x).Select(g => new { Value = g.Key, Count = g.Count() }).Where(s => Rank.Contains("FF"));

can anybody know why third query is not working?

Try using the count() method. It allows you to provide a match expression similar to Where. — Nico
– Nico, Commented Nov 12, 2013 at 7:28

Ondrej Janacek · Accepted Answer · 2013-11-12 07:47:02Z

6

This is nearly correct

var f = Rank.GroupBy(x => x)
            .Select(g => new { Value = g.Key, Count = g.Count() })
            .Where(s => Rank.Contains("FF"));

just change the end to so that you query newly created anonymous objects

var f = Rank.GroupBy(x => x)
            .Select(g => new { Value = g.Key, Count = g.Count() })
            .Where(s => s.Value == "FF");

edited Nov 12, 2013 at 7:47

answered Nov 12, 2013 at 7:28

Ondrej Janacek

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4 Comments

Oliver Over a year ago

i would put the where clause before the select statement just to avoid the creation of not needed anonymous objects, but in that case the where clause should be .Where(g => g.Key.Contains("FF")). Also be aware that there is a big difference between checking for substring (like given in the question code) and checking for equality (like in this answer). So @Vijay should know all the incoming data and know which one works better.

Ondrej Janacek Over a year ago

+1 Good point! My answer just answers his question "why third query is not working".

Vijay Rana Over a year ago

Thanks Oliver for your suggestions. and @Ondrej: i marked your answer because it was really answer of my question but as functionality wise i found Wudzik ans. is more useful so i used his answer in my application.

Ondrej Janacek Over a year ago

@VijayRana Wudzik's code is far better solution, less error-prone when constructing complicated linq queries. As I said, I just answered your questinon so that you know the reason, not just better solution. Turning back on problem does not solve them :)

Kamil Budziewski · Accepted Answer · 2013-11-12 07:27:47Z

4

Try this

var matchCount = Rank.Count(x=>x.Contains("FF"));

it will return count of strings containing "FF" in your list, if you wan't to know if there is any item that matches your predicate, do:

if(Rank.Any(x=>x.Contains("FF"))
{
   ...
}

answered Nov 12, 2013 at 7:27

Kamil Budziewski

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Comments

Hossain Muctadir · Accepted Answer · 2013-11-12 07:33:55Z

0

var list = new List<string>
               {
                   "FF", "ABC", "CC", "FF", "FF"
               };
string search = "FF";

var result = list.GroupBy(l => l).Where(g => g.Key.Contains(search)).Select(s => new Tuple<string, int>(s.Key, s.Count())).FirstOrDefault();

answered Nov 12, 2013 at 7:33

Hossain Muctadir

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