C# application slows Down after 20-30 mins?

Question

I have c# application which reads data from serial port. I have put serial read handler in timer with interval 1 second , because data coming every 1 second on timer I calling

delegate void SetTextCallback(string text);
ReceivedText(serialPort1.ReadExisting());

I also showing received data in richtextbox just to check it getting proper data or not. But after 15-20 mins application slows down wont even respond.

 private void ReceivedText(string text)
 {
        if (this.rtbReceived.InvokeRequired)
        {
            SetTextCallback x = new SetTextCallback(ReceivedText);
            this.Invoke(x, new object[] { (text) });
        }
        else
        {
            this.rtbReceived.Text += text;
            serialdata = text;
            if (serialdata.Length > 0 &&
                serialdata.Length < 42 &&
                serialdata.Contains("#") ||
                serialdata.StartsWith(" #"))
            {
                serialdata.Trim();
                splitdata = serialdata.Split(' ');

                try
                {
                    txtBathTemp.Text = splitdata[3];
                    txtBaroPressure.Text = splitdata[4];

                    double stemp = double.Parse(splitdata[5]);

                    txtSampleTemp.Text = (Math.Round(stemp, 2)).ToString();
                }
                catch (Exception EX)
                { 
                    MessageBox.Show(ex.Message);
                }
            }
        }
    }

Answer 1

There is a chance that this.rtbReceived.Text grows up after some time. Even if it doesn't use huge amount of memory, constantly manipulating String is not efficent. Have you considered using StringBuilder instead?