Can we use overloaded Where operator in LINQ Query?

Question

This sample demonstrates an indexed Where clause that returns digits whose name is shorter than their value. Source Code

public void Linq5() 
{ 
    string[] digits = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" }; 

    var shortDigits = digits.Where((digit, index) => digit.Length < index); 

    Console.WriteLine("Short digits:"); 
    foreach (var d in shortDigits) 
    { 
        Console.WriteLine("The word {0} is shorter than its value.", d); 
    } 
}

Now My Question is ...Can we write this in the LINQ Query format like:

from u in digits where u.Length>index select u;

Here How to get the INDEX value from above Query?

possible duplicate of [LINQ where using index in query language](http://stackoverflow.com/questions/4049773/linq-where-using-index-in-query-language) — Ufuk Hacıoğulları, Dec 20 '12 at 10:01
possible duplicate of http://stackoverflow.com/questions/4049773/linq-where-using-index-in-query-language — Teejay, Dec 20 '12 at 10:01

Sergey Berezovskiy · Answer 1 · 2012-12-20T17:07:28.963

1

No, overloaded Where operator is not available in query syntax. Here is quote from msdn:

In query expression syntax, a where (Visual C#) or Where (Visual Basic) clause translates to an invocation of Where<TSource>(IEnumerable<TSource>, Func<TSource, Boolean>)

You can introduce index manually:

int index = 0;
var query = from u in digits 
            where u.Length > index++ 
            select u;

But keep in mind that you should also manually reset index before each query invocation. Anyway - if you need index, then fluent API is the best choice for you:

var query = digits.Where((u, i) => u.Length > i);

I don't see any reason why not to use it.

edited Dec 20 '12 at 17:07

answered Dec 20 '12 at 10:00

Sergey Berezovskiy

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Thanks...Is there any other option..? – Tanya Samson Dec 20 '12 at 16:58
@user1849388 I've added link to msdn, which points how query syntax translated into Where operator. Problem is that you should pass `Func` to where clause in query syntax. You can't add some additional parameter there. And I'm still don't understand why you don't want to use `Where((u, i) => u.Length > i)` – Sergey Berezovskiy Dec 20 '12 at 17:26

score 0 · Answer 2 · answered Dec 20 '12 at 10:08

0

Try this:

string[] digits = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };

var shortDigits = from pair in digits.Select((digit, index) => new { digit, index })
              where pair.digit.Length < pair.index
              select pair.digit;

answered Dec 20 '12 at 10:08

Salaros

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Thanks a lot. This is what exactly I'm looking for. btw, what is he difference between the Select and Where? I think both operators are doing the same work? – Tanya Samson Dec 21 '12 at 05:53
Select is usually used when you need to iterate ALL the elements of the enumeration and return something for those elements (in my example a pair of values). While Where is usually used to restrict the enumeration to a list of elements that satisfy a given condition. P.S. I my answer was useful for you consider accepting and upvoting it ;) – Salaros Dec 27 '12 at 10:20

Can we use overloaded Where operator in LINQ Query?

2 Answers2