Using CancellationToken in an ASP.NET Web Application

CancellationToken is a feature in .NET that allows tasks to be cancelled gracefully. It is particularly useful in ASP.NET applications where requests may need to be terminated due to user actions, timeouts, or resource limitations. Learn More

Why Use CancellationToken?

1. Improve Performance – Prevent unnecessary resource consumption when a request is abandoned.

2. Handle User Actions – Allow cancellation if a user navigates away or closes the browser.

3. Support Long-Running Processes – Cancel background tasks when no longer needed.

Example Usage in an ASP.NET Controller | Video Tutorial

When handling HTTP requests in ASP.NET Core, you can pass CancellationToken as a parameter:

csharp

[HttpGet("long-operation")]
public async Task<IActionResult> PerformLongOperation(CancellationToken cancellationToken)
{
    try
    {
        // Simulate a long-running task
        await Task.Delay(5000, cancellationToken);
        return Ok("Operation completed successfully");
    }
    catch (OperationCanceledException)
    {
        return StatusCode(499, "Client closed the request");
    }
}

Using CancellationToken in Background Services

If you are running background tasks (e.g., fetching data periodically), use CancellationToken in services:

csharp

public class MyBackgroundService : BackgroundService
{
    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        while (!stoppingToken.IsCancellationRequested)
        {
            // Perform periodic work
            await Task.Delay(1000, stoppingToken);
        }
    }
}

Key Points to Remember

• Always check cancellationToken.IsCancellationRequested inside loops or long-running tasks.

• Catch OperationCanceledException to gracefully handle task cancellation.

• Inject CancellationToken in async methods whenever applicable.

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