C#

Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "PersonList", "PersonList.csproj", "{2B009498-47EB-4A26-B5F4-8A855348065E}"
EndProject

public delegate void SetStringDelegate(string stringToSet);

public class Form1
{
  private void appendStringInTextBoxDelegate(string stringToAppend)
  {
    if (textBox.InvokeRequired)
    {
      this.Invoke(new SetStringDelegate(textBox1.AppendText), new object[] { stringToAppend });
    }
    else
    {
      textBox.AppendText(stringToAppend);
    }
  }

  private void sendAndReceiveButton_Click(object sender, EventArgs e)
  {
    comPort.connect("COM1", appendStringInTextBoxDelegate);
    string myReceivedMessage = comPortSendAndReceive("My send message");
    if (myReceivedMessage != null)
    {
      MessageBox.show("Received the following message: " + myReceivedMessage);
    }
    else
    {
      MessageBox.show("Timeout when reading message");
    }
  }
}

class ComPort
{
  private SetStringDelegate stringReceivedDelegate;
  public void connect(string comPort, SetStringDelegate stringReceivedDelegate)
  {
    // Connect to the com port
    this.stringReceivedDelegate = stringReceivedDelegate;
  }

  public string comPortSendAndReceive(string stringToBeSent)
  {
    // Send the message.
    // Start a timer that will fire if we don't receive the 
    // complete message within a certain amount of time.
    try
    {
      System.Threading.Thread.Sleep(System.Threading.Timeout.Infinite);
    }
    catch (ThreadInterruptedException)
    {
      // If we received a timeout, return null.
      // If we received the complete message, return the complete message and 
      // cancel the timer.
    }
  }

  private void port_DataReceived(object sender, SerialDataReceivedEventArgs e)
  {
    // ALWAYS call stringReceivedDelegate, even if not the 
    // complete message is received.
    // If the COMPLETE message is received, then call Interrupt()
    // on the thread that called comPortSendAndReceive.
  }
}