How does asynchrony differ from parallelism?

Asynchrony is a way of organizing code where time-consuming operations (such as input/output) do not block the execution of the program. An asynchronous method is launched, and control returns to the caller while the operation runs in the background. This allows for efficient resource utilization, especially in single-threaded applications.

Parallelism is the simultaneous execution of multiple tasks, usually on different CPU cores or threads. Parallel tasks truly run concurrently, which speeds up computations.

In C#, asynchrony is often implemented using async/await and Task, allowing the thread not to be blocked, while parallelism is achieved through Parallel, Thread, or Task.Run to perform multiple operations simultaneously.

Example:

// Asynchronous method
async Task<string> DownloadAsync(string url) {
    using var client = new HttpClient();
    return await client.GetStringAsync(url);
}

// Parallel execution
Parallel.For(0, 10, i => {
    Console.WriteLine($"Processing {i} on thread {Thread.CurrentThread.ManagedThreadId}");
});