Can you explain the concept of deferred execution of LINQ results and how it works?

In LINQ (Language Integrated Query) in C#, the concept of deferred (lazy) execution of queries is used. This means that the query itself is not executed at the moment of declaration but only when the result is accessed, for example, during iteration or when calling methods that require materialization (like ToList(), ToArray()).

Deferred execution allows:

• Optimizing performance, as queries are not executed unnecessarily.
• Building complex query chains that are executed in a single pass.

Example:

var numbers = new List<int> {1, 2, 3, 4, 5};
var query = numbers.Where(n => n > 3); // Query declared but not executed

foreach(var num in query) // Query is executed here
{
    Console.WriteLine(num); // Will output 4 and 5
}

If the collection numbers is modified after declaring the query but before execution, the result will reflect the changes, as the query executes at the moment of enumeration.