The following is the clsMaths class declaration is:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
 
namespace UseDelegate
{
    class clsMaths
    {
        public delegate int PointerMaths(int i, int y);//declare delegate
        public PointerMaths getPointer(int intOperate) //definition delegate object
        {
            PointerMaths objpointer = null;
            if (intOperate==1)
            {
                 objpointer = Add;
            }
            else if (intOperate==2)
            {
                objpointer= Sub;
            }
            else if (intOperate==3)
            {
                objpointer = Multi;
            }
            else if (intOperate==4)
            {
                objpointer = Div;
            }
            return objpointer;
        }
 
        #region  Maths Methods
        private int Add(int i, int y)
        {
            return i + y;
        }
        private int Sub(int i, int y)
        {
            return i - y;
        }
        private int Multi(int i, int y)
        {
            return i * y;
        }
        private int Div(int i, int y)
        {
            return i / y;
        }
#endregion
    }
 
} 

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
 
namespace UseDelegate
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
            clsMaths objMath = new clsMaths();
            int intOperatio = Convert.ToInt32(textBox3.Text);
            int intNumber1 = Convert.ToInt32(textBox1.Text);
            int intNumber2 = Convert.ToInt32(textBox2.Text);
            int intResult =objMath.getPointer(intOperatio).Invoke(intNumber1, intNumber2);  //Invoke:for delegate to call method
 
            label1.Text= "Result Is:"+intResult.ToString();
        }
    }
}

Let's look atoperating results: