Async and Await

async/await let code that waits on something slow (a network call, a file read) do so without blocking the calling thread — directly parallel to JavaScript's async/await.

async Task<string> FetchDataAsync() {
    using var client = new HttpClient();
    return await client.GetStringAsync("https://api.example.com/data");
}

async Task Main() {
    Console.WriteLine("Starting...");
    string data = await FetchDataAsync();
    Console.WriteLine(data);
}

A method marked async returns a Task (or Task<T>) — a placeholder for a result that isn't ready yet, exactly like a JavaScript Promise. await pauses that method (without blocking the thread) until the Task completes.

Common mistakes

• Calling .Result or .Wait() on a Task instead of awaiting it — this blocks the calling thread and can cause a deadlock in some contexts (notably older ASP.NET and UI applications).
• Forgetting await on an async call entirely — the call starts but the calling code moves on without its result, and any exception it throws goes unobserved.