c# events

1) Create the event in Customer class. The <TYPE> can be string, decimal, bool, class, etc. 

public event EventHandler<decimal> OverdraftEvent; 

2) Place code to trigger the event.

public void MakePayment (decimal amount)

{ 

    if (amount < accountFunds)   // Not enough. Create event trigger. 

           OverdraftEvent?.Invoke(this, amount);

}

3) Create listeners for the event. Attached methods to run when event is triggered. You can place the event listeners in different classes/places as needed. 

private void WireUpForm()

{

    customer.Checking.OverdraftEvent += CheckingAccount_OverdraftEvent;

}

4) Create method that is run when event is triggered. 

private void CheckingAccount_OverdraftEvent(object sender, decimal e)

{

    // do something to handle event ... for example:

    errorMessage.Text = $"Not enough funds available for your {string.Format("{0:C2}", e)} transaction";

}

5) Remove listeners when app is closing. Else, the app may not fully close and get stuck in memory with no garbage collect. This leads to memory leaks !

customer.Checking.OverdraftEvent -= CheckingAccount_OverdraftEvent;