C#

public class StreamWrapper<T> where T : Stream
{
    private T stream;

    public T Stream
    {
        get { return this.stream; }
        set { this.stream = value; }
    }
}

public class FileStreamWrapper : StreamWrapper<FileStream>
{
    public FileStreamWrapper()
    { }
}

FileStreamWrapper fsw = new FileStreamWrapper();
fsw.Stream = new FileStream(...);

public class Class_a {
       public virtual Stream Property { get; set; }
   }

public class Class_b : Class_a {
       public new FileStream Property { get; set; }
   }

"Simplicity carried to the extreme becomes elegance."
-Jon Franklin

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

namespace TestClass_a
{
    public interface IStream
    {
        Stream Property { get; set; }
    }

    public class Class_a : IStream
    {
        private Stream _stream = null;

        public Stream Property
        {
            get { return _stream; }
            set { _stream = value; }
        }
    }

    public class Class_b : Class_a, IStream
    {
        public FileStream Property
        {
            get { return (FileStream)base.Property; }
            set { base.Property = (Stream)value; }
        }

        #region IStream Members

        Stream IStream.Property
        {
            get { return base.Property; }
            set { base.Property = value; }
        }

        #endregion
    }

    class Program
    {
        static void Main(string[] args)
        {
            Class_a a = new Class_a();
            a.Property = new MemoryStream();
            Class_b b = new Class_b();
            b.Property = File.Open("C:\\test.txt", FileMode.OpenOrCreate);
            Class_a b2 = b;
            bool canRead = b2.Property.CanRead;
        }
    }
}

Sameera Afzal wrote:

in C language