serial port working and get result but not asyncronus by timer why

Can any one helping me in this code :
using System;
using System.IO.Ports;
using System.Windows.Forms;
using System.Threading;
using System.Text;

namespace CommSample
{
public partial class Form1 : Form
{
string portData = "";
public Form1()
{
InitializeComponent();
}

void Application_Idle(object sender, EventArgs e)
{
label3.Text = serialPort1.IsOpen ? "[Open]" : "[Closed]";
}

private void button1_Click(object sender, EventArgs e)
{
if (pollingCheckbox.Checked)
{
timer1.Enabled = true;
}
else
{
timer1.Enabled = false;
TransmitCommand();
}
}

private void TransmitCommand()
{
if (textBox1.Text.Length > 0)
{
if (serialPort1.IsOpen)
{
serialPort1.Write("SX" + "\r");

}
}
}

private void ClosePort()
{
if (serialPort1.IsOpen)
{
TransmitCommand();
serialPort1.DataReceived -= new SerialDataReceivedEventHandler(serialPort1_DataReceived);
serialPort1.Close();
}
}

private void closePortToolStripMenuItem_Click(object sender, EventArgs e)
{
ClosePort();
}

private void exitToolStripMenuItem_Click(object sender, EventArgs e)
{
Close();
}

private void Form1_Load(object sender, EventArgs e)
{
serialPort1.PortName = Properties.Settings.Default.Port;
serialPort1.BaudRate = Properties.Settings.Default.Baud;
serialPort1.DataBits = Properties.Settings.Default.DataBits;
serialPort1.Parity = (Parity)Enum.Parse(typeof(Parity), Properties.Settings.Default.Parity);
serialPort1.StopBits = (StopBits)Enum.Parse(typeof(StopBits), Properties.Settings.Default.StopBits);

Application.Idle += new EventHandler(Application_Idle);
}

private void OpenPort()
{
serialPort1.Open();
serialPort1.DataReceived += new SerialDataReceivedEventHandler(serialPort1_DataReceived);
timer1.Enabled = true;
}

private void openPortToolStripMenuItem_Click(object sender, EventArgs e)
{
OpenPort();
label4.Visible = true;
label5.Visible = true;
}

private void optionsToolStripMenuItem_Click(object sender, EventArgs e)
{
ClosePort();

using (Form2 form = new Form2())
{
if (form.ShowDialog(this) == DialogResult.OK)
{
serialPort1.PortName = Properties.Settings.Default.Port;
serialPort1.BaudRate = Properties.Settings.Default.Baud;
serialPort1.DataBits = Properties.Settings.Default.DataBits;
serialPort1.Parity = (Parity)Enum.Parse(typeof(Parity), Properties.Settings.Default.Parity);
serialPort1.StopBits = (StopBits)Enum.Parse(typeof(StopBits), Properties.Settings.Default.StopBits);
}
}
}

void serialPort1_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
string debugMessage = "";
float value;
if (!InvokeRequired)
{
if (e.EventType == SerialData.Chars)
{
portData += serialPort1.ReadExisting();
while (portData.Contains("\r"))
{
string temp = portData.Substring(0, portData.IndexOf('\r'));

foreach (byte x in Encoding.UTF8.GetBytes(portData))
{
debugMessage = debugMessage + x.ToString("x2");
}
Console.WriteLine("Debug : " + debugMessage);

portData = portData.Substring(portData.IndexOf('\r') + 1);
if (temp.Length == 12)
{
char status = temp[11];
switch (status)
{
case ' ':
if (float.TryParse(temp.Substring(1, 8).Trim(), out value))
{
//enter code here to process integer
textBox2.Text = temp.Substring(1, 8).Trim();
Console.WriteLine("Parse Number : {0}", textBox2.Text);
}
else
{
textBox2.Text = "Not Numeric";
Console.WriteLine("Cannot parse : {0}", portData);
}
break;
case 'I':
textBox2.Text = "Invalid";
Console.WriteLine("Invalid : {0}", portData);
break;
case 'M':
textBox2.Text = "In Motion";
Console.WriteLine("In Motion : {0}", portData);
break;
case 'O':
textBox2.Text = "Under/Over Range";
Console.WriteLine("Uneder/Over : {0}", portData);
break;
}
}
}
}
}

else
{
SerialDataReceivedEventHandler invoker = new SerialDataReceivedEventHandler(serialPort1_DataReceived);
BeginInvoke(invoker, new object[] { sender, e });
}

}



private void pollingCheckbox_CheckedChanged(object sender, EventArgs e)
{
if (timer1.Enabled && !pollingCheckbox.Checked)
{
timer1.Enabled = false;
}
}

private void timer1_Tick(object sender, EventArgs e)
{
if (pollingCheckbox.Checked)
{
TransmitCommand();
}
}

}
}
Notes : textbox2 in multiline mode and my weight bridge weighting is ricelake IQ+355
This is code above working good his result is ok according to weight bridge value
but it is not asyncronusly
i make timer is enabled but also it is not asyncronusly meaning you need close application and open again to take the value of weight bridge
Now How i make code above asyncronusly working and changes when weight bridge in same time
thanks

Can nay one help me in this code above
why timer not work
why code not work asynchronously
if possible help me
thanks

You need to add breakpoints to your code, to stop it. Somewhere along the line, you'll see something that you weren't expecting. That's probably the only way to find the error. Otherwise, look at some other samples online