Simple Calculator using a Class in C#

using System.Diagnostics;
using System;
using System.Xml.Linq;
using System.Windows.Forms;
using System.Collections;
using System.Drawing;
using System.Data;
using System.Collections.Generic;
using System.Linq;
 
 
namespace MDAS
{
	public class calculate
	{
		//declare a private variable as a double
		private double _num1;
		private double _num2;
		private double _total;
 
		//set a readonly property for the total of the MDAS
		public double total
		{
			get
			{
				return _total; //return the total
			}
		}
		//create a property for a private variable so that you can access it
		public double num1
		{
			get
			{
				return _num1; //return the first value
			}
			set
			{
				_num1 = value; //set the first value
			}
		}
		public double num2
		{
			get
			{
				return _num2;
			}
			set
			{
				_num2 = value;
			}
		}
 
		//create the sub procedures of the MDAS
		public void multiply()
		{
			//formula of multiplication
			_total = num1 * num2;
		}
		public void divide()
		{
			//formula of division
			_total = num1 / num2;
		}
		public void add()
		{
			//formula of addition
			_total = num1 + num2;
		}
		public void subtract()
		{
			//formula of subtraction
			_total = num1 - num2;
		}
 
 
	}
 
}

using System.Diagnostics;
using System;
using System.Xml.Linq;
using System.Windows.Forms;
using System.Collections;
using System.Drawing;
using System.Data;
using System.Collections.Generic;
using System.Linq;
 
 
 
namespace MDAS
{
	public partial class Form1
	{
		public Form1()
		{
			InitializeComponent();
		}
 
		//create a sub procedure for the events of clicking the radio button that handles all of it.
		public void RadioButton_Click(object sender, System.EventArgs e)
		{
 
			//call a constructor method and return to cal as an instance of a class
			calculate cal = new calculate();
 
			//declaring the string variable represent as a textbox
			string txtnum1 = TextBox1.Text;
			string txtnum2 = TextBox2.Text;
			//declaring the double variable
			double dbl_val1 = default(double);
			double dbl_val2 = default(double);
 
			if (Information.IsNumeric(txtnum1) && Information.IsNumeric(txtnum2)) //check if the textbox has a numeric value
			{
				//convert the string to double
				dbl_val1 = double.Parse(txtnum1);
				dbl_val2 = double.Parse(txtnum2);
 
				//get the value of the converted variable
				//to pass it into the variable in the class
				cal.num1 = dbl_val1;
				cal.num2 = dbl_val2;
 
				//the condition is, if the radiobutton is clicked,
				//the operation of MDAS executes.
				if (Radio_Multiplication.Checked)
				{
					//result:
					cal.multiply(); //call a subname in a class for multiplying
				}
				else if (Radio_Division.Checked)
				{
					//result:
					cal.divide(); //call a subname in a class for dividing
				}
				else if (Radio_Addition.Checked)
				{
					//result:
					cal.add(); //call a subname in a class for adding
				}
				else if (Radio_Subtaction.Checked)
				{
					//result:
					cal.subtract(); //call a subname in a class for subtracting
				}
			}
			else
			{
				//the result is:
				//if the textbox is empty or has a string value
				TextBox3.Text = "Enter a number";
				return ;
			}
			//put the result of the MDAS to a textbox.
			TextBox3.Text = cal.total.ToString();
		}
 
 
	}
 
}