How do I make use of a parameter in a ElapsedEventHandler (Timer)?

Question

List<System.Timers.Timer> myTimers = new List<System.Timers.Timer>();
    
private void startFunction()
{    
    for (var parameter = 0; parameter < list.Count; parameter++)
    {
        System.Timers.Timer timer = new System.Timers.Timer(TimeSpan.FromMinutes(10).TotalMilliseconds);

        timer.Elapsed += new ElapsedEventHandler(someFunction);
        timer.Start();
        myTimers.Add(timer);
    }
}

// without the int parameter this code works 
public void someFunction(object sender, ElapsedEventArgs e, int parameter) 
{
    // some code that have to run over time
}

So on the someFunction method I used a parameter (int) and without it, this is working out fine. I just want to send a parameter through this function and with searching online and trying different methods it still does not work.

Anyone having knowledge on how to send a parameter using the function someFunction every 10 minutes?

you can't, the event simply has only the eventargs available. How would you imagine the timer to infer the value for that parameter - it has no clue that param even exists. How is that param populated? Where do you set it and where do you use it? I suppose it has nothing to do with the timer at all. — MakePeaceGreatAgain, Mar 28 '22 at 12:11
I left that out because I didn't want to write to much code in this example to be more clarified but it seems to be mistake — Ando, Mar 28 '22 at 12:19
In that case, just do `timer.Elasped += (o, e) => someFunction(o, e, parameter);`. The lambda you supply to `Elapsed` captures the variable `parameter`, and will then pass it to `someFunction` when it's invoked — canton7, Mar 28 '22 at 12:25
better way could be encapsule the timer and your parameter as some class. — Lei Yang, Mar 29 '22 at 00:51

canton7 · Accepted Answer · 2022-03-28T12:59:27.833

1

Since parameter is just a local variable, you can create a lambda which captures this variable, and passes it to your someFunction method.

private void startFunction()
{    
    for (var parameter = 0; parameter < list.Count; parameter++)
    {
        var timer = new System.Timers.Timer(TimeSpan.FromMinutes((10)).TotalMilliseconds);

        int parameterCopy = parameter;
        timer.Elapsed += (o, e) => someFunction(o, e, parameterCopy);
        timer.Start();
        myTimers.Add(timer);
    }
}

The parameterCopy is required because of this issue.

edited Mar 28 '22 at 12:59

answered Mar 28 '22 at 12:28

canton7

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This sadly didn't work out for me – Ando Mar 28 '22 at 12:35
@Ando Why not? It probably means that there's critical information missing from your question, but we need to understand what that is before we can help – canton7 Mar 28 '22 at 12:35
maybe the important information can be that the code above someFunction is also in their own function. And that int parameter is from a list.Count and have to be different for every item in that list.. – Ando Mar 28 '22 at 12:39
@Ando Well it's a simple local variable in your question, and there's no "also in their own function", so could you fix your question please? I answered the question as asked – canton7 Mar 28 '22 at 12:41
@Ando Thanks. It's currently not valid C# however -- it's not possible to nest a `public void` method inside another method. Can you make sure your question actually contains your real code please? – canton7 Mar 28 '22 at 12:51
minor mistakes while editing – Ando Mar 28 '22 at 12:56
@Ando Right, but nested functions in C# *are* a thing, so it's not clear whether the mistake is the nesting, or the presence of the `public` – canton7 Mar 28 '22 at 12:58
@Ando See my edit – canton7 Mar 28 '22 at 12:59
1

excuse me, I did another test and your method seems to work indeed! thank you! – Ando Mar 29 '22 at 06:48

How do I make use of a parameter in a ElapsedEventHandler (Timer)?

1 Answers1