定时任务无法停止

1. 使用Cancellation Token来取消定时任务：

public async Task MyScheduledJobAsync(CancellationToken cancellationToken)
{
    while (!cancellationToken.IsCancellationRequested)
    {
        // 进行定时任务的操作
        await Task.Delay(TimeSpan.FromMinutes(30), cancellationToken);
    }
}

2. 使用Task.Run来启动定时任务并使用CancellationTokenSource.Stop来停止任务：

private CancellationTokenSource _cancellationTokenSource;

public void StartScheduledJob()
{
    _cancellationTokenSource = new CancellationTokenSource();
    Task.Run(() => MyScheduledJobAsync(_cancellationTokenSource.Token), _cancellationTokenSource.Token);
}

public void StopScheduledJob()
{
    _cancellationTokenSource.Cancel();
}