What syntax is this when setting the Elapsed property?

Question

Can someone explain me what this System.Timer does with the ElapsedEventHandler? I don't understand this syntax:

private readonly System.Timers.Timer _timer7 = new System.Timers.Timer();
this._timer7.Elapsed += (ElapsedEventHandler) ((A_1, A_2) =>
      {
        this._logger.LoggingOfError("T7-Timeout");
      });

funny I asked the exact same question 3 years ago..... [here I found it](https://stackoverflow.com/questions/37679480/please-explain-timer-event-async-await-syntax). It's about an async handler, but basically I had the same question about the syntax. If it answers your question, I can mark it as duplicate — Mong Zhu, Sep 19 '19 at 14:27

score 0 · Answer 1 · answered Sep 19 '19 at 14:33

The code of your question is the same as:

_timer7.Elapsed += (sender, e) =>
{
  _logger.LoggingOfError("T7-Timeout");
};

And that is the same as:

_timer7.Elapsed += _timer7_Elapsed;

private void _timer7_Elapsed(object sender, System.Timers.ElapsedEventArgs e)
{
  _logger.LoggingOfError("T7-Timeout");
}

You can have explanations about anonymous methods here:

What are anonymous methods in C#?

score 0 · Answer 2 · answered Sep 19 '19 at 14:53

System.Timers.Elapsed is type of ElapsedEventHandler which defined as below:

public delegate void ElapsedEventHandler(object sender, ElapsedEventArgs e);

the delegate registered for _timer7.Elapsed is a Lambda Expression (anonymous method).

A_1 is sender, and A_2 is e.

As a result, when _timer7.Elapsed will fired, the anonymous method with arguments A_1 as sender, and A_2 as e, will be called.
That will lead the line this._logger.LoggingOfError("T7-Timeout"); to be execute

1

thanks! This helped me a lot – Josh Sep 19 '19 at 15:11

What syntax is this when setting the Elapsed property?

2 Answers2