IHostedService in C# doesn't trigger method every time?

Question

This is my code in .net core 5 which wants to trigger a function every 2 minutes. I don't know why LoadData function doesn't get triggered after 2 minutes and only get triggered the first time?

public Task StartAsync(CancellationToken stoppingToken)
{
    var _timer = new System.Threading.Timer(LoadData, null, TimeSpan.Zero, TimeSpan.FromMinutes(2));

    return Task.CompletedTask;
}

private async void LoadData(object state)
{
   var res = await _repository.GetAsync();
   //....
}

Answer 1

The following line:

var _timer = new System.Threading.Timer(LoadData, null, TimeSpan.Zero, TimeSpan.FromMinutes(2));

Will create a timer and save the reference only to local variable, allowing the GC to collect the System.Threading.Timer. Workaround can be to introduce a field:

System.Threading.Timer _timer;

public Task StartAsync(CancellationToken stoppingToken)
{
    _timer = new System.Threading.Timer(LoadData, null, TimeSpan.Zero, TimeSpan.FromMinutes(2));

    return Task.CompletedTask;
}

Also switching to System.Timers.Timer could also work (but have not tested it).

See also:

• Can Timers get automatically garbage collected?
• Why does a System.Timers.Timer survive GC but not System.Threading.Timer?