Async streams with IAsyncEnumerable in C Sharp (C#) - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is IAsyncEnumerable<T> used for in C#?

IAsyncEnumerable<T> allows you to create asynchronous streams of data that can be consumed with await foreach. It helps process data as it arrives without blocking the program.

beginner

How do you consume an async stream from IAsyncEnumerable<T>?

You use await foreach to loop through the async stream, which lets you wait for each item asynchronously as it becomes available.

beginner

Write the signature of a method that returns an async stream of integers.

public async IAsyncEnumerable<int> GetNumbersAsync()

intermediate

What keyword is used inside an async stream method to yield values one by one?

The yield return keyword is used to asynchronously produce each item in the stream.

intermediate

Why are async streams useful compared to returning a full collection at once?

<p>Async streams let you start processing data immediately as it arrives, which saves memory and improves responsiveness, especially for large or slow data sources.</p>

Which keyword do you use to iterate over an IAsyncEnumerable<T>?

A foreach

B for

C await foreach

D while

You must use await foreach to asynchronously iterate over an IAsyncEnumerable<T>.

What does IAsyncEnumerable<T> represent?

A A synchronous collection

B A task that returns a list

C A delegate for async methods

D An asynchronous stream of data

IAsyncEnumerable<T> represents an asynchronous stream of data that can be awaited item by item.

Which keyword is used inside an async stream method to produce each item?

A return

B yield return

C await return

D yield await

The yield return keyword is used to produce each item in an async stream.

What is the benefit of using async streams?

A They allow processing data as it arrives without blocking

B They block the thread until all data is ready

C They convert synchronous code to asynchronous automatically

D They cache all data before returning

Async streams allow processing data as it arrives without blocking the program.

Which C# version introduced IAsyncEnumerable<T>?

A C# 8.0

B C# 10.0

C C# 9.0

D C# 7.0

IAsyncEnumerable<T> was introduced in C# 8.0.

Explain how to create and consume an async stream using IAsyncEnumerable<T> in C#.

Think about how you produce items one by one and how you read them asynchronously.

Describe the advantages of using async streams over returning a full collection at once.

Consider how waiting for all data before processing can slow down your program.