Async and await keywords in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the async keyword do in C#?

The async keyword marks a method as asynchronous, allowing it to run operations without blocking the main thread. It enables the use of await inside the method.

beginner

What is the purpose of the await keyword?

await pauses the execution of an async method until the awaited task completes, without blocking the thread. It helps write asynchronous code that looks like synchronous code.

intermediate

Can an async method return void?

Yes, but only for event handlers. Normally, async methods return Task or Task<T> to allow callers to await them and handle exceptions.

intermediate

What happens if you forget to use await inside an async method?

The method will run synchronously until it hits an awaited task. If you don't use await, the method may complete early and not wait for asynchronous operations, causing bugs.

beginner

Why is using async and await better than blocking calls?

They keep the app responsive by not blocking threads. This is like waiting for a friend without stopping everything else you do, improving performance and user experience.

What keyword do you use to mark a method as asynchronous in C#?

A thread

B await

C task

D async

The async keyword marks a method as asynchronous.

What does the await keyword do?

A Blocks the thread until the task finishes

B Pauses the async method without blocking the thread

C Starts a new thread

D Cancels a running task

await pauses the async method but does not block the thread.

Which return type is common for async methods?

A Task or Task<T>

B int

C string

D void

Async methods usually return Task or Task<T>.

What happens if you call an async method but do not use await?

A The method runs synchronously and waits

B The program crashes

C The method runs asynchronously but caller does not wait

D The method is ignored

Without await, the caller does not wait for the async method to finish.

Why should you avoid blocking calls in UI applications?

A They freeze the UI and make it unresponsive

B They keep the UI responsive

C They improve performance

D They use less memory

Blocking calls freeze the UI, making the app unresponsive.

Explain how async and await work together in C# to keep applications responsive.

Think about waiting for a task without stopping everything else.

Describe the common return types of async methods and why they are important.

Consider how the caller knows when the async work is done.