Async Programming in .NET | MSDN Documentation

Asynchronous Programming in .NET

Asynchronous programming enables applications to remain responsive while performing long-running operations such as I/O, network calls, or CPU‑bound work. The .NET Framework provides the Task‑based Asynchronous Pattern (TAP) and the async/await keywords to simplify this model.

Key Concepts

Task – Represents an asynchronous operation.
async – Marks a method as asynchronous.
await – Suspends execution until the awaited task completes.
ConfigureAwait – Controls context capture.

Task‑Based Asynchronous Pattern (TAP)

TAP standardizes method signatures for asynchronous operations:

// Example of a TAP method
public Task<int> GetDataAsync(CancellationToken token = default)
{
    return Task.Run(() =>
    {
        // Simulate work
        Thread.Sleep(2000);
        return 42;
    }, token);
}

Using async and await

The async modifier enables the await keyword inside a method. The compiler rewrites the method into a state machine.

public async Task ProcessAsync()
{
    var data = await GetDataAsync();
    Console.WriteLine($"Result: {data}");
}

Best Practices

Prefer async all the way down the call stack.
Avoid blocking calls such as Task.Wait() or .Result.
Cancel long‑running operations with CancellationToken.
Use ConfigureAwait(false) in library code to avoid deadlocks.

Common Pitfalls

Forgetting to propagate async leads to “fire‑and‑forget” bugs.
Deadlocks caused by synchronously waiting on async code in UI contexts.
Excessive thread‑pool usage when using Task.Run for CPU‑bound work.