# Deferred Execution

*noun*

say it: **“dih-FERD ek-sih-KYOO-shun”** **/dɪˈfɜːrd ˌɛksɪˈkjuːʃən/**

A LINQ query running only when its results are used, not when it is written.

## What is **Deferred Execution** in C#?

**Deferred Execution** — A LINQ query isn't run when you write it, only when you use its results: in a `foreach`, or with `ToList()` or `Count()`. Change the list in between and the query sees the change.

```csharp
List<int> scores = [21, 14];
IEnumerable<int> high = scores.Where(s => s > 20); // nothing runs yet
scores.Add(35);
Console.WriteLine(high.Count()); // 2
```

## In a sentence

- “Because of **deferred execution**, the query saw the score I added after writing it.”

Level: Freelancer · [More C# terms at this level](https://www.ask-codey.com/glossary?category=c-sharp&level=4)

Updated: October 28, 2026

Source: https://www.ask-codey.com/glossary/deferred-execution