Deferred execution behavior in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is deferred execution in C#?

Deferred execution means that the evaluation of a query or expression is delayed until its results are actually needed, not when the query is defined.

beginner

Which C# feature commonly uses deferred execution?

LINQ queries use deferred execution, meaning the query runs only when you iterate over the results, like with a foreach loop.

intermediate

How does deferred execution help with performance?

It avoids unnecessary work by only computing results when needed, which can save time and memory if the results are never used or only partially used.

intermediate

What happens if the data source changes after defining a deferred query but before iterating it?

Because execution is deferred, the query reflects the current state of the data source at the time of iteration, not when the query was defined.

intermediate

How can you force immediate execution of a deferred query in C#?

You can force immediate execution by calling methods like ToList(), ToArray(), or Count(), which evaluate the query right away.

What does deferred execution mean in C# LINQ?

A The query runs only when you iterate over its results

B The query runs immediately when defined

C The query runs only once at compile time

D The query runs only when the program starts

Deferred execution means the query is not executed until you actually use its results, such as in a foreach loop.

Which method forces immediate execution of a LINQ query?

A Where()

B OrderBy()

C Select()

D ToList()

ToList() forces the query to run immediately and stores the results in a list.

If the data source changes after defining a deferred query but before iterating it, what happens?

A The query results reflect the updated data source state

B The query results reflect the original data source state

C The query throws an error

D The query results are empty

Deferred execution means the query runs at iteration time, so it uses the current state of the data source.

Why is deferred execution useful?

A It makes the program run slower

B It forces all queries to run at program start

C It avoids unnecessary computation until results are needed

D It caches all query results permanently

Deferred execution delays work until necessary, improving efficiency.

Which of these LINQ methods does NOT cause immediate execution?

A Count()

B Select()

C ToList()

D ToArray()

Select() is a query operator that uses deferred execution; it does not execute immediately.

Explain deferred execution in C# and how it affects when a LINQ query runs.

Think about when the query results are actually created.

Describe how changing the data source after defining a deferred query impacts the query results.

When does the query get evaluated?