      private void button3_Click(object sender, EventArgs e)
        {
            if (textBox1.Text != "")
            {
                input = new FileStream("Student.Rnd", FileMode.Open, FileAccess.Read);
                binaryInput = new BinaryReader(input);
                int stno = Convert.ToInt32(textBox1.Text);
                if (stno > 0 && stno < NUMBER_OF_REC)
                {
                    input.Seek((stno - 1) * randomAccessRecord.SIZE, 0);
                    record.StNo = binaryInput.ReadInt32();
                    record.fName = binaryInput.ReadString();
                    record.lName = binaryInput.ReadString();
                    record.Grade = binaryInput.ReadDouble();
                    textBox2.Text = record.fName;
                    textBox3.Text = record.lName;
                    textBox4.Text = record.Grade.ToString();
                }
                else
                    MessageBox.Show("Invalid stNo");
                input.Close();
            }
            else
                MessageBox.Show("Please enter stNo");
        }
