C# – Serial Port ReadLine vs ReadExisting or how to read the data from serial port properly

I am reading data from serial port. The data comes off the scale. I am now using Readline() and getting data dropped even after I removed DiscardInBuffer().

What is the proper way to read the data from the serial port? There are so few examples online that I feel it's like some holy grail that no one has figured out.

C#, WinCE 5.0, HP thin client, Compact framework 2.0

 private void WeighSample()
    {
        this._processingDone = false;
        this._workerThread = new Thread(CaptureWeight);
        this._workerThread.IsBackground = true;
        this._workerThread.Start();
    } //end of WeighSample()


    private void CaptureWeight()
    {
         globalCounter++;
         string value = "";


          while (!this._processingDone)
          {
              try
              {

                 value = this._sp.ReadLine();

                  if (value != "")
                  {
                      if (value == "ES")
                      {
                          _sp.DiscardInBuffer();
                          value = "";
                      }
                      else
                      {
                          this.Invoke(this.OnDataAcquiredEvent, new object[] { value });
                      }
                  }
              }
              catch (TimeoutException)
              {
                  //catch it but do nothing
              }
              catch
              {
                  //reset the port here?
                  MessageBox.Show("some other than timeout exception thrown while reading serial port");
              }
          }


    } //end of CaptureWeight()

One thing to note about my application is that I start the thread (weighSample) when the cursor jumps onto the textbox. The reason to this is that the weight can also be typed in manually (part of the requirements). So I don't know in advance whether a user is going to press PRINT on the balance or type the weight. In either case after the data is acquired, I exit the worker thread. Also, note that I am not using serial port event DataReceived, since I have been told it's not reliable.

This is my first experience with serial ports.