C#不使用反射机制如何为委托添加事件

接口：

public delegate int ChildEventHandle(object arg1, object arg2);
    public interface IChildEvent
    {
        event ChildEventHandle add;
    }

ChildPage继承接口：

class ChildPage: Window,IChildEvent
    {
#pragma warning disable
        public MainWindow parentWindow;
        public event ChildEventHandle add;
        public event ChildEventHandle sub;
        public event ChildEventHandle mulity;
#pragma warning restore
        protected virtual void AddEvent(object arg1, object arg2)
        {
            //实例化委托对象，发起调用
            ChildEventHandle handle = add;
            if (arg1.GetType().ToString() == "System.Int32" && arg2.GetType().ToString() == "System.Int32")
                handle(arg1, arg2);
            else MessageBox.Show("参数输入有误，请重新输入！！");
        }
}

WindowChild继承ChildPage

public partial class WindowChild : ChildPage
    {
        public WindowChild()
        {
            InitializeComponent();
            base.parentWindow = this;
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            //调用父类中已经默认实现的类发起事件
            base.AddEvent(txtBox1.Text, txtBox2.Text);
        }       
    }

报错如下，我应该怎么添加事件处理函数呢：

public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            WindowChild son = new WindowChild();
            //定义真正的事件处理函数，通过lamba表达式
           //son.add+=????????报错，找不到add
        }
    }