Base and Sealed class

base class field

using System;

public class Animal
{
    public string color = "white";
}

public class Dog:Animal{
    string color="black";

public void showColor()
{

    Console.WriteLine(base.color);
    Console.WriteLine(color);
}
}

namespace baseKeyword
{

    public class TestBase
    {
        static void Main(string[] args)
        {
            Dog d=new Dog();
            d.showColor();
            Console.ReadKey();
        }
    }
}

//base class method

using System;

namespace BaseClassMethod
{
    public class Animal
    {
        public virtual void eat()
        {
            Console.WriteLine("eat");
        }
    }

    public class Dog : Animal
    {
        public override void eat()
        {
            base.eat();
            Console.WriteLine("eating bread!");

        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Dog d = new Dog();
            d.eat();
            Console.ReadKey();
        }
    }
}

//calling base class constructor internally

using System;

namespace base_class_constructor_internally
{

    public class Animal
    {

        public Animal()
        {
            Console.WriteLine("Animal");
        }
       
    }


    public class Dog : Animal
    {
        public Dog()
        {
            Console.WriteLine("Dog...");
        }
    }


    class Program
    {
        static void Main(string[] args)
        {

            Dog d=new Dog();
            Console.ReadLine();
        }
    }
}

//sealed class
using System;

namespace Sealed
{
    sealed public class Animal
    {
        public void eat()
        {
            Console.WriteLine("Eating...");
        }
    }

    public class Dog : Animal
    {
        public void bark()
        {
            Console.WriteLine("Barking....");
        }
    }

    public class TestSealed 
    {
        static void Main(string[] args)
        {
            Dog d=new Dog();
            d.bark();
            d.eat();
            Console.ReadLine();

        }
    }
}

using System;


namespace SealedMethod
{
    public class Animal
    {
        public virtual void eat()
        {
            Console.WriteLine("eating..");
        }

        public virtual void run()
        {
            Console.WriteLine("running...");
        }
    }


    public class Dog : Animal
    {
        public void eat()
        {
            Console.WriteLine("Eating bread...");
        }

        public sealed void run()
        {
            Console.WriteLine("Running very fast");
        }
    }

    public class BabyDog : Dog
    {
        public override void eat()
        {
            Console.WriteLine("Eating biscuits");
        }

        public override void run()
        {
            Console.WriteLine("Running slowly");
        }
    }

    
    class Program
    {
        static void Main(string[] args)
        {
            BabyDog d=new BabyDog();
            d.eat();
            d.run();
            Console.ReadKey();
        }
    }
}

Sealed variable not possible:

using System;


namespace SealedMethod
{
    public class Animal
    {
        public virtual void eat()
        {
            Console.WriteLine("eating..");
        }

        public virtual void run()
        {
            Console.WriteLine("running...");
        }
    }


    public class Dog : Animal
    {
        public void eat()
        {
            Console.WriteLine("Eating bread...");
        }

        public void run()
        {
            Console.WriteLine("Running very fast");
        }
    }

    public class BabyDog : Dog
    {
        public override void eat()
        {
            Console.WriteLine("Eating biscuits");
        }

        public override void run()
        {
            Console.WriteLine("Running slowly");
        }
    }

    
    class Program
    {
        static void Main(string[] args)
        {
            BabyDog d=new BabyDog();
            d.eat();
            d.run();

            sealed int x=10;
            Console.WriteLine(x);

            Console.ReadKey();
        }
    }
}