Async and Await in C# – Asynchronous Programming

1Why Do We Need Async and Await?

Hi friends! In this article, we will learn async and await in C#. These keywords help us execute time-consuming operations without blocking the calling thread. For example, when an application calls an API, reads a file or queries a database, it can continue handling other work while waiting for the result. This makes applications more responsive and improves scalability, especially in ASP.NET Core Web APIs.

2Think About Booking a Train Ticket

Imagine booking a train ticket using an application. After clicking Book, the application sends a request to the railway server.

While the server checks seat availability and processes payment, you don't want the entire application to freeze. You can continue interacting with the application.

Similarly, C# uses async and await to wait for operations such as database calls and HTTP requests without blocking the current thread.

3Understand These Important Keywords

1. async

The async keyword marks a method as asynchronous. It allows us to use await inside that method.

2. await

The await keyword waits for an asynchronous operation to complete. It does not block the thread while the operation is waiting.

3. Task

Task represents an asynchronous operation that may complete in the future. Task<T> represents an operation that returns a value of type T.

4. Task.Delay()

Task.Delay() asynchronously waits for a specified duration. We use it here to simulate a time-consuming operation.

4Let's Build an Async C# Program

Let's create a console application that checks an order status. The application waits for the simulated server response and then displays the result.

using System;
using System.Threading.Tasks;

class Program
{
    static async Task Main()
    {
        Console.WriteLine("Checking order...");

        string status =
            await GetOrderStatusAsync();

        Console.WriteLine($"Order status: {status}");
        Console.WriteLine("Thank you!");
    }

    static async Task<string>
        GetOrderStatusAsync()
    {
        await Task.Delay(2000);
        return "Shipped";
    }
}

Here, Main is asynchronous. It calls GetOrderStatusAsync(), which waits for two seconds using Task.Delay(). After completion, it returns the order status.

5What Will the Console Display?

The first message appears immediately. After the asynchronous operation completes, the remaining messages are displayed.

Checking order...
Order status: Shipped
Thank you!

The order status appears only after the awaited operation completes.

6Watch Async Code Run in VS Code

Follow how the program executes, waits for the asynchronous operation and displays the final result.

7Let's Revise What We Learned

Async and await help us write responsive applications. They are especially useful when working with databases, external APIs and file operations.

Remember these three key takeaways:

• async: Marks a method as asynchronous.
• await: Asynchronously waits for an operation to finish.
• Task: Represents an asynchronous operation.

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