What are the differences between asynchronous and multithreading

Asynchronous and multithreading are completely different concepts in C#. Asynchronously pay attention to task execution order, and multithreads pay attention to task execution in parallel. Asynchronous operations avoid blocking the current thread by coordinating task execution, while multithreads execute tasks in parallel by creating new threads. Asynchronous is more suitable for I/O-intensive tasks, while multithreading is more suitable for CPU-intensive tasks. In practical applications, asynchronous and multithreading are often used to optimize program performance. Pay attention to avoid deadlocks, excessive use of asynchronous, and rational use of thread pools.

C# asynchronous and multithreading: Do you really understand the difference between them?

Many people think that asynchronous and multi-threading are similar, and even use these two words in a mixed way, which is not the case. They are two completely different concepts in C#. Only by understanding their differences can you write more efficient and elegant code. In this article, I will explain their differences in a simple and easy way, and share some of the experience I have accumulated in my years of programming career and the pitfalls I have stepped on.

Let’s talk about the conclusion first: asynchronous is about the execution order of tasks, and multithreading is about the parallel execution of tasks. Asynchronous operations do not block the current thread, while multithreads create new threads to execute tasks in parallel. This may seem simple, but it contains huge differences.

Let’s review the basics first. C#'s multithreading depends on the thread management mechanism provided by the operating system, and each thread has its own stack and context. Creating and managing threads is expensive, and thread context switching will also bring performance losses. Asynchronous operations are essentially implemented based on async and await keywords. They do not rely on new threads, but use the asynchronous programming model (APM) or task parallel library (TPL) to coordinate the execution of tasks.

So, how does asynchronous work? Imagine a scenario where you send a request to a server and wait for the server to return the result. Using multithreading, you create a new thread to send the request and wait for the result, the main thread blocks and waits. Using asynchronous, you will return immediately after sending the request. When the server returns the result, the system will notify your program to continue to perform subsequent operations. During this period, the main thread is not blocked and can continue to process other tasks. This is exactly the charm of asynchronousness!

Let’s take a look at a simple example and experience the elegance of asynchronous:

 <code class="csharp">// 多线程版本private void LongRunningTask_Multithreading() { Thread thread = new Thread(() => { // 模拟耗时操作Thread.Sleep(5000); Console.WriteLine("Multithreading task completed."); }); thread.Start(); Console.WriteLine("Multithreading task started."); } // 异步版本private async void LongRunningTask_Async() { await Task.Delay(5000); Console.WriteLine("Async task completed."); Console.WriteLine("Async task started."); }</code>

This code simulates a 5-second operation. The multi-threaded version blocks the main thread until the child thread has completed execution. The asynchronous version does not, and the main thread can continue to perform other tasks.

Advanced asynchronous usage involves Task.WhenAll , Task.WhenAny and other methods, which can achieve more complex asynchronous operation coordination. It should be noted that the await keyword can only be used in the async method, and the tasks behind await must be of Task or Task<t></t> type.

Common errors? Many developers mistakenly believe that asynchronousness equals high performance. In fact, asynchronous is more suitable for I/O-intensive tasks, such as network requests, file reading and writing. For CPU-intensive tasks, multithreading has more advantages. Blindly using asynchronously may reduce performance due to a large number of context switching. In addition, debugging of asynchronous code is also relatively complicated and requires certain experience and skills. Remember, choosing asynchronous or multi-threaded depends on your specific needs and scenarios.

In terms of performance optimization, in addition to choosing the appropriate solution, you also need to pay attention to avoiding deadlocks, avoiding excessive asynchronous use, and rationally utilizing thread pools. Code readability and maintainability are also very important, and it is recommended to use meaningful variable names and clear code structure.

Finally, I want to emphasize that asynchronous and multithreading are not mutually exclusive. In practical applications, the two are often used in combination to optimize program performance. Only by understanding their differences and characteristics can we better control them and write better and more efficient C# code. This requires continuous learning and practice in order to truly become a C# expert!

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