Example:

using System;
using System.IO;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            byte[] b2 = new byte[6];

            FileStream f1;
            FileStream f2;

            f1 = new FileStream("abc.txt", FileMode.Open, FileAccess.Read);
            f2 = new FileStream("xyz.txt", FileMode.Open, FileAccess.Write);

            if (f1.CanSeek)
                Console.WriteLine("Yes, It can be seeked.");
            else
                Console.WriteLine("Yes, It can not seeked.");


            f1.Close();

            if (f2.CanSeek)
                Console.WriteLine("Yes, It can be seeked.");
            else
                Console.WriteLine("Yes, It can not seeked.");


            f2.Close();
        }
    }
}

Output

Yes, It can be seeked.
Yes, It can be seeked.

In above program, we need to remember, when we use "FileStream" class then we need to include System.IO namespace in the program.