Insertion at the begining of a Linklist in C#

using System;
using System.Collections.Generic;
using System.Text;

namespace ConsoleApplication38
{
class node
{
public int delete;
public int data;/*it will store the data*/
public node link;/*it will hold the address of the next memory location where the data is stored*/
}
class Program
{
/*these are the variables */
public static node START;
public static node LASt;
public static node CURRENT;
public Program()
{
START = null;
LASt = null;
}
public void insertionbegin()
{
node newnode = new node();
Console.WriteLine("Enter the data");
newnode.data = int.Parse(Console.ReadLine());
newnode.link = START;
START = newnode;
Console.WriteLine("DAta has been inserted");

}

public void displaynode()
{
Console.WriteLine("Data in the list are");
CURRENT = START;
while (CURRENT != null)
{
Console.WriteLine(CURRENT.data);
CURRENT = CURRENT.link;
}
Console.ReadLine();

}

static void Main(string[] args)

{
Program obj = new Program();
do
{
Console.Clear();
Console.WriteLine("********************************************");
Console.WriteLine("** MAIN MENU *****************");
Console.WriteLine("**************************************");
Console.WriteLine("*1.Inserting at the end of the list******");
Console.WriteLine("*2.Insertion at the begining of the list****");
Console.WriteLine("*3.Display the list *******************");
Console.WriteLine("*4.Exit ****************");
Console.WriteLine("*********************************************");
Console.WriteLine("\nEnter ur choice");
int choice = int.Parse(Console.ReadLine());
switch (choice)
{
case 1: { break; }
case 2: { obj.insertionbegin(); break; }
case 3: { obj.displaynode(); break; }
case 4: { break; }
default: { Console.WriteLine("Invalid option"); break; }
}
} while (true);
Console.ReadLine();

}
}
}