C# 取消订阅计时器事件不起作用

Question

[Inject]
public Timer timer { get; set; }

protected override void OnInitialized()
{
    settingsModel = applicationDb.SettingsModal.FirstOrDefault();
    updateInfo();
}

public async void updateInfo()
{
    try
    {
        if (settingsModel.Message != "" && settingsModel.Message != null)
        {
            timer.Elapsed -= (w, e) => timer_Elapsed(w,e);
            timer.Elapsed += (w, e) => timer_Elapsed(w, e);          
            timer.Interval = 3000;
            timer.Start();
        }
        else
        {
            timer.Elapsed -= (w, e) => timer_Elapsed(w, e);

            timer.Stop();
        }
    }
    catch (Exception e)
    {
        ToastService.ShowError(e.Message);
    }
}

async void timer_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{       
    // do some stuff
}

The problem is unsubscribe not working on this line

timer.Elapsed -= new System.Timers.ElapsedEventHandler(timer_Elapsed);

Each time the UpdateInfo method gets called, the event timer.Elapsed gets more sub

Answer 1

Subscribe to the method instead of an anonymous function.

// Subscribe
timer.Elapsed += timer_Elapsed; 

// Unsubscribe
timer.Elapsed -= timer_Elapsed;

From this page on subscribing to events .

If you don't have to unsubscribe from an event later, you can use the addition assignment operator (+=) to attach an anonymous function as an event handler.

You cannot easily unsubscribe from an event if you used an anonymous function to subscribe to it.

We recommend that you don't use anonymous functions to subscribe to events if you have to unsubscribe from the event at some later point in your code.