Why base class object refers its own methods, although referring to memory address of child class

Question

 
using System;
using System.Collections.Generic;
using System.Text;
namespace ConsoleApplication1
{
       class basecalss
    {
        public  void virtual_method()
        {
            Console.WriteLine("Virtual in baseclass");
        }
    }
    class derivedclass1 : basecalss
    {
        public  void virtual_method()
        {
            Console.WriteLine("Override in dervied class1");
        }
    }
   
    class implement_override  
    {
        public static void Main()
        {
            basecalss baseobj;
            derivedclass1 derobj1 = new derivedclass1();
            baseobj = derobj1;
            baseobj.virtual_method();
            Console.ReadLine();
                 
        }
    }
}
-------------------------------------------------------

Output is: Virtual in baseclass
As per the code,
Baseclass object refers child class object, assigned the memory address of Child class.
  baseobj.virtual_method();
When we call above, why it calls method of baseclass, although it refers to memory location of child class. Obviously we have not used virtual/override concepts. Point is that if base refers memory address of child, it should not refer its own methods.