SimpleSerial Communication: Are my cmd codes correct for .NET 2.0 framewwork

using System; 
2.using System.Collections.Generic; 
3.using System.ComponentModel; 
4.using System.Data; 
5.using System.Drawing; 
6.using System.Text; 
7.using System.Windows.Forms; 
8.using System.IO.Ports; 
9.using System.Threading; 
10. 
11.namespace SimpleSerial 
12.{
13.
14.     public partial class Form1 : Form 
15.     { 
16.         // Add this variable  
17.         string RxString; 
18.         string stx = "\u0002"; 
19.         string etx = "\u0003"; 
20.  
21.        
22.         public Form1() 
23.         { 
24.             InitializeComponent(); 
25.         } 
26. 
27.         private void buttonStart_Click(object sender, EventArgs e) 
28.         { 
29.             serialPort1.PortName = "COM3"; 
30.             serialPort1.BaudRate = 9600; 
31.             serialPort1.Parity = Parity.None; 
32.             serialPort1.DataBits = 8; 
33.             serialPort1.StopBits = StopBits.One; 
34.             serialPort1.Handshake = Handshake.None; 
35.                
36.             serialPort1.Open(); 
37.             if (serialPort1.IsOpen) 
38.             { 
39.                 buttonStart.Enabled = false; 
40.                 buttonStop.Enabled = true; 
41.                 textBox1.ReadOnly = false; 
42.             } 
43.         } 
44. 
45.         private void linkLabel_HC1_100_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e) 
46.         { 
47.             if (serialPort1.IsOpen) 
48.             { 
49.                 serialPort1.Write(stx + "01P00102##" + etx); 
50.             } 
51.         } 
52.
53.         private void buttonStop_Click(object sender, EventArgs e) 
54.         { 
55.             if (serialPort1.IsOpen) 
56.             { 
57.                 serialPort1.Close(); 
58.                 buttonStart.Enabled = true; 
59.                 buttonStop.Enabled = false; 
60.                 textBox1.ReadOnly = true; 
61.             } 
62. 
63.         } 
64. 
65.         private void Form1_FormClosing(object sender, FormClosingEventArgs e) 
66.         { 
67.             if (serialPort1.IsOpen) serialPort1.Close(); 
68.         } 
69. 
70.         private void textBox1_KeyPress(object sender, KeyPressEventArgs e) 
71.         { 
72.             // If the port is closed, don't try to send a character. 
73.            if (!serialPort1.IsOpen) return; 
74.
75.             // If the port is Open, declare a char[] array with 1 element. 
76.             char[] buff = new char[1]; 
77.
78.             // Load element 0 with the key character. 
79.             buff[0] = e.KeyChar; 
80.
81.             // Send the 1 character buffer. 
82.             serialPort1.Write(buff, 0, 1); 
83.
84.             // Set the KeyPress event as handled so the character won't 
85.             // display locally. If you want it to display, omit the next line. 
86.             e.Handled = false; 
87.         } 
88.
89.         private void DisplayText(object sender, EventArgs e) 
90.         { 
91.             textBox1.AppendText(RxString); 
92.         } 
93.
94.         private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e) 
95.         { 
96.             RxString = serialPort1.ReadExisting(); 
97.             this.Invoke(new EventHandler(DisplayText)); 
98.         } 
99.      } 
100.}