Written by Sujith Quintelier • Oct 15, 2025

Mastering Asynchronous Programming with C# async/await - Part 5: Real-World Use Cases

Real-world async use cases: HttpClient APIs, file IO, EF Core queries, responsive UI handlers, and background hosted services.

Oct 15, 2025

Part 5: Real-World Use Cases

We’ve covered the foundations, pitfalls, and async patterns. Now let’s see how async/await shows up in real applications — from APIs to UI apps.

Use Case 1: Calling Web APIs with `HttpClient`

HttpClient is fully async, making it ideal for network calls.

public async Task GetWeatherAsync()
{
    var client = new HttpClient();
    var response = await client.GetStringAsync("https://api.weather.com/data");
    Console.WriteLine(response);
}

This avoids blocking threads while waiting for the response.

Use Case 2: File I/O

The System.IO namespace supports async methods:

public async Task WriteFileAsync(string path, string content)
{
    await File.WriteAllTextAsync(path, content);
}

Similarly, reading large files:

public async Task<string> ReadFileAsync(string path)
{
    return await File.ReadAllTextAsync(path);
}

This keeps applications responsive even with big files.

Use Case 3: Database Access with EF Core

Entity Framework Core has async APIs for queries:

var users = await db.Users.Where(u => u.IsActive).ToListAsync();

This is critical in ASP.NET Core apps — the thread isn’t blocked while waiting for the database.

Use Case 4: Responsive UIs

In WPF or WinForms, async keeps the UI thread free:

private async void Button_Click(object sender, EventArgs e)
{
    StatusLabel.Text = "Loading...";
    var data = await GetDataAsync();
    StatusLabel.Text = $"Done: {data}";
}

Without async, the UI would freeze until the task completes.

Use Case 5: Background Services

In ASP.NET Core, background tasks are implemented with IHostedService:

public class Worker : BackgroundService
{
    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        while (!stoppingToken.IsCancellationRequested)
        {
            Console.WriteLine("Worker running...");
            await Task.Delay(1000, stoppingToken);
        }
    }
}