如何手动取消 .NET 核心 IHostedService 后台任务？

Question

I want to do some async work after Startup.cs is finished. I've implemented some async tasks in a background service by extending BackgroundService .

My question is how to cancel the task from running at a time when I determine? I can only see examples in the documentation for delaying the next cycle.

I've tried to manually execute StopAsync but the while loop executes forever (the token is not cancelled, even though I feel like it should be, because I've passed the token to StopAsync and the implementation looks like that's what it's meant to do).

Here is some simplified code:

public class MyBackgroundService : BackgroundService
{
    private readonly ILogger<MyBackgroundService> _logger;

    public MyBackgroundService(ILogger<MyBackgroundService> logger)
    {
        _logger = logger;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        _logger.LogInformation("MyBackgroundService is starting.");

        while (!stoppingToken.IsCancellationRequested)
        {
            _logger.LogInformation("MyBackgroundService task doing background work.");

            var success = await DoOperation();
            if (!success)
            {
                // Try again in 5 seconds
                await Task.Delay(5000, stoppingToken);
                continue;
            }

            await StopAsync(stoppingToken);
        }
    }
}

Answer 1

I didn't quite catch on to the fact that ExecuteAsync is only called once by the framework. So the answer is simply to break out of the loop when you're done.

protected override async Task ExecuteAsync(CancellationToken stoppingToken)
{
    _logger.LogInformation("MyBackgroundService is starting.");

    while (!stoppingToken.IsCancellationRequested)
    {
        _logger.LogInformation("MyBackgroundService task doing background work.");

        var success = await DoOperation();
        if (!success)
        {
            // Try again in 5 seconds
            await Task.Delay(5000, stoppingToken);
            continue;
        }

        break;
    }
}