How to use C# BinaryReader class?

static void WriteMe() {
   using (BinaryWriter w = new BinaryWriter(File.Open("C:\abc.txt", FileMode.Create))) {
      w.Write(25.9);
      w.Write("DEMO DATA");
   }
}

static void ReadMe() {
   using (BinaryReader r = new BinaryReader(File.Open("C:\abc.txt", FileMode.Open))) {
      Console.WriteLine("Value : " + r.ReadDouble());
      Console.WriteLine("Value : " + r.ReadString());
   }
}

static void Main(string[] args) {
   WriteMe();
   ReadMe();
   Console.ReadKey();
}