c# - "Cross thread operation not valid" .. while reading data on Serial Port

In a windows form application, on main form load, i have set a serial port and started reading it. The purpose is, as and when I receive some data on the serial port, I want to open another form related to the data.

So i use the DataReceived Event Handler of the serial port.

  void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)

        {

            string str = this.serialPort1.ReadLine();


                if (!string.IsNullOrEmpty(str))
                {


                    Main.Instance.customerData = new CustomerData(str);

                    Main.Instance.customerData.MdiParent = Main.Instance;  //Exeption received at this point
                    Main.Instance.customerData.Disposed += new EventHandler(customerData_Disposed);

                    Main.Instance.customerData.Show();


                }

        }

But when I try to open a form within the event handler it gives me an InvalidOperationExeption saying:
"Cross-thread operation not valid: Control 'Main' accessed from a thread other than the thread it was created on."

I tried removing the code line :
Main.Instance.customerData.MdiParent = Main.Instance;
then it works fine. But its necessary also to assign the mdiparent in order to open it as a child form.

Any suggestions to resolve this problem ?

Answer

Use the Invoke method on the Main form. You have to pass control over to the Main form to interact with it. The event handler is triggered on a background thread.

Here's some sample code that may work:

void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
    string str = this.serialPort1.ReadLine();
    if (!string.IsNullOrEmpty(str))
    {
        ShowCustomerData(str);

    }   

}

private delegate void ShowCustomerDataDelegate(string s);

private void ShowCustomerData(string s)
{
    if (Main.Instance.InvokeRequired)
    {

        Main.Instance.Invoke(new ShowCustomerDataDelegate(ShowCustomerData), s);
    }
    else
    {

        Main.Instance.customerData = new CustomerData(str);
        Main.Instance.customerData.MdiParent = Main.Instance;  //Exeption received at this point
        Main.Instance.customerData.Disposed += new EventHandler(customerData_Disposed);

        Main.Instance.customerData.Show();

    }
}