Serial Ports in C# ReadExisting() issue?

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C#

serial-port

Hi All,

Just going through, debugging a program that uses

.ReadExisting()

I was wondering if this is why some of the data comes in irregularly i.e. it does not see the delimiter and the end of the string back from the unit.
I was wondering about using the ReadTo method i.e.

.ReadTo(">");

as the data sent is appended with a ">" but trying this yesterday led to a lot of trouble and crashed PC (I'm starting to suspect the board "but it works with HyperTerminal so it must be your code" quote). The routine I am using for send receive is detailed at the bottom it is called with the following means

string ReadData;
        Reply_Status = (int)REPLY.NO_REPLY;
        ReadData = Write_Outstring(Command);

HELP!
Glenn

private string Write_Outstring(Data_To_Unit)
        {
            string Data_From_Unit = "";

            Reply_Status = (int)REPLY.NO_REPLY;
            rtbCommsRecord.Text += Data_To_Unit + "\n";

            myComPort.Write(Data_To_Unit + (char)10 + (char)13);
            {
                while (Reply_Status == (int)REPLY.NO_REPLY)
                {
                    NoDataAtPort.Enabled = true;
                }
                NoDataAtPort.Enabled = false;

                if (Reply_Status == (int)REPLY.TIMEOUT_REPLY)
                {
                    Data_From_PitStop = "TIMEOUT\n";
                }
                else if (Reply_Status == (int)REPLY.YES_REPLY)

                {
                    Data_From_Unit = myComPort.ReadExisting();
                    rtbCommsRecord.Text += Data_From_Unit; // +"\n";
                    rtbIncoming.Text = Data_From_Unit;

                    //                rtbLogged.Text +=ReplyData;
                    if (Data_From_Unit.Contains("UD:"))
                    {
                        // rtbReturnedData.Text += Data_From_Unit + '\n' + '\r';
                        rtbUnlistedData.Text += Data_From_Unit+ '\n';// + '\r'; here is the problem
                    }

                    if (Data_From_Unit.Contains("LD:"))
                    {
                        // rtbReturnedData.Text += Data_From_Unit + '\n' + '\r';
                        rtbListedData.Text += Data_From_Unit;// +'\n';// + '\r';
                    }
                    if (Data_From_Unit.Contains("OK"))
                    {
                        rtbLogged.Text += rtbIncoming.Text;
                    }
                    rtbLogged.Text += rtbIncoming.Text;
                }
                else
                {
                    MessageBox.Show("ERROR IN Pitstop Comms\n");
                    Reply_Status = (int)REPLY.NO_REPLY;
                }
            }

            return (Data_From_Unit);


        }

UPDATE: The Data being returned by ReadExisting() is not complete I found this by sticking a message box to slow/stop comms flow, I think I need an example of how to the above with .ReadTo() which will cause problems if I use .ReadTo(">") some data returns "\n\r>" and some other parts return ">\r>" would .ReadTo(\r and >) be possible?

Glenn