C# async and await

Asynchronous programming in C# is a technique used to perform tasks without blocking the main execution thread, allowing other operations to continue running concurrently. This is particularly useful when performing time-consuming operations, like file I/O, network requests, or database operations, without freezing the user interface (UI) or blocking other processes.

In C#, asynchronous programming is typically achieved using the async and await keywords.

async Keyword

1. The async keyword is used to define a method as asynchronous.

2. An asynchronous method typically returns a Task (or Task for methods that return a value). This indicates the method is non-blocking and will complete at some point in the future.

3. When a method is marked async, you can use the await keyword inside the method.

public async Task AsyncMethod()
{
    // Asynchronous operations here
}

await keyword

1. The await keyword is used to “pause” the execution of an asynchronous method until a Task is complete, but it doesn’t block the thread.

2. It can only be used inside an async method.

3. await is used with tasks like Task.Run, Task.Delay, or other asynchronous operations, and it lets the compiler know to wait for the task to finish before continuing the execution of the method.

public async Task MyAsyncMethod()
{
    // Non-blocking operation
    await Task.Delay(1000);  // Simulate some asynchronous work (1 seconds delay)
    Console.WriteLine("Finished waiting!");
}

Example:

using System;
using System.Threading.Tasks;

public class MyProgram
{
    public static async Task Main(string[] args)
    {
        // Run a series of async operations in a for loop
        await MyAsyncOperations();
    }

    public static async Task MyAsyncOperations()
    {
        // Use a for loop to simulate multiple asynchronous operations
        for (int i = 1; i <= 5; i++)
        {
            Console.WriteLine($"Starting task {i}");
            // Await an asynchronous task (simulating a delay)
            await Task.Delay(1000); // Simulate a 1-second task
            Console.WriteLine($"Task {i} completed");
        }
    }
}

Explanation:

1. The MyAsyncOperations method is async, meaning we can use await inside it.
2. The for loop runs 5 iterations (simulating 5 tasks).
3. Inside the loop, we simulate an asynchronous operation (like a network request or I/O operation) using Task.Delay(1000). This simulates a delay of 1 second.
4. await ensures that the program waits for each asynchronous task to complete before moving on to the next iteration of the loop.

Output: