how write/read data into serial port in smartdevice using C#

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C#

hi friends
i write code for serial port in smart device using C# in that i can connect/disconnect the Available ports but I cant send the data to serial port and read also I tried this code please help me it very urgent
in my code having
i used Two Labels in that
one Label for Available COM Ports
second Label for connect and disconnect show on this label
one combox
three buttons (connect,disconnect,send)
one Rich text box
one text box

//THSI IS SMART DEVICE PROJECT USING c#

public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        SerialPort port = new SerialPort();
        private void Form1_Load(object sender, EventArgs e)
        {
            try
            {
                #region Display all available COM Ports
                string[] ports = SerialPort.GetPortNames();
                // Add all port names to the combo box:
                foreach (string port in ports)
                {
                    //this.cboPortName.Items.Add(port);
                    this.cbbCOMPorts.Items.Add(port);
                }
                #endregion
                this.btnDisconnect.Enabled = false;
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
        private void btnConnect_Click_1(object sender, EventArgs e)
        {
            if (port.IsOpen)
            {
                port.Close();
            }
            try
            {
                {
                    port.PortName = cbbCOMPorts.Text;
                    port.BaudRate = 96000;
                    port.Parity = Parity.None;
                    port.DataBits = 8;
                    port.StopBits = StopBits.One;
                }
                //.Encoding = System.Text.Encoding.Unicode 
                port.Open();
                lblMessage.Text = cbbCOMPorts.Text + " Connected. ";
                btnConnect.Enabled = false;
                btnDisconnect.Enabled = true;
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            txtDataToSend.Focus();
        }
        private void btnDisconnect_Click_1(object sender, EventArgs e)
        {
            try
            {
                port.Close();
                lblMessage.Text = port.PortName + " disconnected.";
                btnConnect.Enabled = true;
                btnDisconnect.Enabled = false;
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
        private void btnSend_Click(object sender, EventArgs e)
        {
            try
            {
                port.Write(txtDataToSend.Text);
               //port.writline(txtDataToSend.Text);

                //txtDataReceived->IS a data Received Text Box name 
               //txtDataToSend->is a data send Text Box name

       txtDataReceived.Text = txtDataReceived.Text + txtDataToSend.Text;
                txtDataReceived.ScrollToCaret();
               }
               txtDataToSend.Text = string.Empty;
           }
           catch (Exception ex)
           {
               MessageBox.Show(ex.Message);
           }
       }