where in query
Learn where in query syntax.
where in a query
In query syntax, where filters elements. It comes after from and before select. The predicate is a bool expression over the range variable: from n in numbers where n > 3 select n.
Multiple conditions can be joined with && and ||. Only elements that satisfy the predicate proceed in the query. You can write multiple where clauses; other clauses may appear between them.
The predicate expression
where takes any bool expression over the range variable. It can be a comparison (n > 3), a method call (n.IsValid()) or a combination.
Join two predicates with && to keep elements that satisfy both; with || to keep elements that satisfy either. Parentheses set precedence: where (n > 0 && n < 10) || n == 100.
Exercise Filter even numbers with where
Filter even numbers in the numbers array using where n % 2 == 0. Iterate with foreach and print each element with Console.WriteLine(n).
Show example solution
Write from n in numbers where n % 2 == 0 select n;. Then loop with foreach (var n in query) { Console.WriteLine(n); }.
Example solution:
using System;
using System.Linq;
class Program
{
static void Main()
{
int[] numbers = { 1, 2, 3, 4, 5, 6 };
var query = from n in numbers
where n % 2 == 0
select n;
foreach (var n in query)
{
Console.WriteLine(n);
}
}
}Test yourself
-
Complete the where clause
var query = from n in numbers ____ n > 3 select n;Show answer
var query = from n in numbers where n > 3 select n; -
Which is a valid where usage?
from n in numbers where n > 0 select n- from n in numbers where n > 0
- where n > 0 from n in numbers select n
- from n in numbers where n > 0 select n
- from n in numbers select n where n > 0
Show answer
from n in numbers where n > 0 select n — Correct. where comes after from and before select.
-
Match the clause to its position
- from
- First (start)
- where
- Predicate (filter)
- orderby
- Middle (sort)
- select
- Last (projection)