Check out example codes for "delegate c# mvc". It will help you in understanding the concepts better.

Code Example 1

using System;
namespace MVC
    public class Book
        // declare a delegate for the bookpricechanged event
        public delegate void BookPriceChangedHandler(objectsender,
        BookPriceChangedEventArgs e);
        // declare the bookpricechanged event using the bookpricechangeddelegate
        public event BookPriceChangedHandlerBookPriceChanged;
        // instance variable for book price
        object _bookPrice;
        // property for book price
        public object BookPrice
                // set the instance variable
                // the price changed so fire the event!
        // method to fire price canged event delegate with proper name
        // this is the method our observers should be implenting!
        protected void OnBookPriceChanged()
            BookPriceChanged(this, new BookPriceChangedEventArgs(_bookPrice));

Learn ReactJs, React Native from