Interface With Events

In a recent WPF application I had to map multiple clickable items under one singular list of clickable items. I chose to create a unifying interface for them. The issue was that I wanted to attach event functions to each item and for this I needed to expose the events at the interface layer. It’s like this that I discovered 2 new keywords “add” and “remove“

The example below  is a console application but it explains the procedure.

Let’s start by creating the delegate for our event

 public class MoneyTransferedArgs : EventArgs
    {
        public double ValueTransferred { get; set; }
    }

    public delegate void MoneyTransferHandler(object sender, MoneyTransferedArgs args);

We now create a base class from which other child classes may inherit. The base class has an event which will be the base event for child classes

public abstract class Bank
    {
        public event MoneyTransferHandler MoneyTransferred;

        public Bank()
        {
            this.MoneyTransferred += (sender, args) =>
            {
                Console.WriteLine("Money Transferred : {0}", args.ValueTransferred);
            };
        }

        public virtual void TransferMoney(double amount)
        {
            this.MoneyTransferred?.Invoke(this, new MoneyTransferedArgs { ValueTransferred = amount });
        }
    }

Child classes will be mandated to implement similar events that will only lead to base class event

public interface IBankLocation
    {
        event MoneyTransferHandler OnMoneyTransferred;

        void TransferMoney(double amount);
    }
 public class BankLocation1 : Bank , IBankLocation
    {
        public event MoneyTransferHandler OnMoneyTransferred
        {
            add => this.MoneyTransferred += value;
            remove => this.MoneyTransferred -= value;
        }
    }
    public class BankLocation2 : Bank, IBankLocation
    {
        public event MoneyTransferHandler OnMoneyTransferred
        {
            add => this.MoneyTransferred += value;
            remove => this.MoneyTransferred -= value;
        }
    }

public abstract class  static void Main(string[] args)
        {
            IBankLocation bankRo1 = new BankLocation1();
            IBankLocation bankRo2 = new BankLocation2();

            bankRo1.OnMoneyTransferred += (s, e) => Console.WriteLine("Sent With BankRo1");
            bankRo2.OnMoneyTransferred += (s, e) => Console.WriteLine("Sent With BankRo2");

            bankRo1.TransferMoney(20);
            bankRo2.TransferMoney(21);
        }