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Deferred operators

Context: Deferred operators (e.g., Where, Select, OrderBy) do not execute until the query is enumerated. They return an IEnumerable<T>.

var deferred = numbers.Where(n => n > 2); // no execution
// Execution happens here
foreach (var item in deferred) { }

List of common deferred operators

Where, Select, SelectMany
Take, Skip
OrderBy, OrderByDescending, ThenBy
GroupBy, Join, GroupJoin
Concat, Distinct, Union, Intersect, Except

Real-world usage example

Complex query composition: Deferred execution allows you to build queries conditionally without performance penalty until the final enumeration.

Example: In EF Core, all IQueryable operators are deferred until ToList() or foreach.