Answer
Deferred execution means a query is not evaluated when it is defined. • Enumeration triggers execution. • Enumerating again can rerun the query and observe changed source data. • Materializing with ToList, ToArray, or similar operators executes immediately.
💡 C# Example
var numbers = new List<int> { 1, 2 };
var query = numbers.Where(number => number > 1);
numbers.Add(3);
Console.WriteLine(string.Join(", ", query));
Output
2, 3
⚡ Quick Revision
Deferred LINQ queries execute when enumerated, not when declared.