Use Async and Await in C#

An async function can contain an await expression, that pauses the execution of the function and waits for the passed Promise's resolution, and then resumes the async function's execution and returns the resolved value. Using the asynchronous approach, the applications continue with other tasks as well.

Quick Navigation

1. Introduction to the async function C#

A method in C# is made an asynchronous method using the async keyword in the method signature. You can have one or more await keywords inside an async method. The await keyword is used to denote the suspension point. An async method in C# can have any one of these return types: Task, Task, and void.

What is the use of Async? Asynchronous programming is a form of parallel programming that allows a unit of work to run separately from the primary application thread. When the work is complete, it notifies the main thread (as well as whether the work was completed or failed).

2. The use of async and await in C#

Async and await are the code markers, which mark code positions from where the control should resume after a task completes. Let's start with practical examples for understanding the programming concept. We are going to take a console Application for our demonstration.

What is the point of async await? Async/await allows making complicated asynchronous code look as simple as synchronous one. It makes writing asynchronous code enormously easier. As you noted in your own question, it looks as if you were writing the synchronous variant - but it's actually asynchronous.

3. Difference between async and await in C#?

First, await causes nothing to run, nothing to be "scheduled". The scheduling (if any) and running (if any) are already in progress before you get to the await. await is an "asynchronous wait"; that is, it asynchronously waits for the task to complete. "Asynchronous" here means "without blocking the current thread".

What does the await keyword do? The await operator is applied to a task in an asynchronous method to suspend the execution of the method until the awaited task completes. The task represents ongoing work. That means the await operator blocks the execution of the for a loop until it gets a response from the server, making it sequential.

4. Why do I use await in C#?

await operator in the Main method In earlier C# versions, to ensure that the Main method waits for the completion of an asynchronous operation, you can retrieve the value of the Task<TResult>. Result property of the Task<TResult> instance that is returned by the corresponding async method.

5. How to use asynchronous?

If you use the async keyword before a function definition, you can then use await within the function. When you await a promise, the function is paused in a non-blocking way until the promise settles. If the promise is fulfilled, you get the value back. If the promise rejects, the rejected value is thrown.

6. Introduction to the async task

AsyncTask is an abstract Android class that helps Android applications handle the Main UI thread in an efficient way. AsyncTask class allows us to perform long-lasting tasks/background operations and show the result on the UI thread without affecting the main thread.

7. Introduction to the Async API

Synchronous/asynchronous APIs are application programming interfaces that return data for requests either immediately or at a later time, respectively. Asynchronous requests are useful in maintaining functionality in an application rather than tying up application resources waiting on a request.

8. Introduction to the callback methods in C#

A callback is a function that will be called when a process is done executing a specific task. The usage of a callback is usually in asynchronous logic. To create a callback in C#, you need to store a function address inside a variable. This is achieved using a delegate or the new lambda semantic Func or Action.

9. Why do I use threads in C#?

Thread class is used for working with threads. It allows creating and accessing individual threads in a multithreaded application. The first thread to be executed in a process is called the main thread. When a C# program starts execution, the main thread is automatically created.

10. What is the async keyword in C#?

Use the async modifier to specify that a method, lambda expression, or anonymous method is asynchronous. If you use this modifier on a method or expression, it's referred to as an async method. The following example defines an async method named ExampleMethodAsync: C# Copy.

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