Rich textbox and string differing

Question

Hi All First question I am reading a serial port and putting output to a string but the string is blank however if I stick a message box in it causes enough of a gap to allow the text to appear in the string. I am using a delay based on the length of the expected reply. The line of code that appears is reply = rtbIncoming.text. rtbIncoming.Text has a string in it from the device. Is it because of seperate threads the reply in the text box appears on one thread there is not enough of a delay for it to get from the comms thread to the UI thread? Glenn

Vulpes · Answer

The Invoke method is synchronous and will therefore block the thread until it completes. You could try using BeginInvoke instead which is asynchronous and therefore returns immediately: this.BeginInvoke(new MethodInvoker(delegate() { rtbIncoming.Text = reply; }));

Vulpes · Answer

Funnily enough I recommended the following very good threading resource to some one else today. I've also added a good resource on delegates and events: http://www.albahari.com/threading/ http://www.akadia.com/services/dotnet_delegates_and_events.html

Glenn Patton · Answer

Hi Vulpes Been in the lab for an hour or so so didn't see your reply in the past I have only used BeginInvoke and was a little unsure of Invoke but with the previous changes & that one the program now responds correctly. this.BeginInvoke(new MethodInvoker(delegate() { rtbIncoming.Text = reply; })); I do really need to understand the delegate methods better & threading as a whole better could you recomend any resource? Glenn

Glenn Patton · Answer

Hmmm It looks like if I only enable the button once it has finished it gets around the problem.... Need my PC to go into one it's hard drive grinding moments..... Glenn

Glenn Patton · Answer

Hi Spotted a problem if the machine is busy (mine was hammering the hard drive!) obviously the invoke method is very dependant on the use of the processor! Is there a source of info that (MircoSoft) is regaurded as official. As this I would like to check to see if there is a system legal way of making it a higher priority to always fire. This is getting away from my area of speciality into the Windows domain (beyond that point lies madness!) Glenn

Glenn Patton · Answer

Hi Vulpes Same guy different forum (I can't be the only person to mess with Serial Ports though!) to give you an update some problems with the board mean that testing can only be done on one part of the board but it 'Works!!!' thank you I just moved where I was declaring the delegate etc. this.Invoke(new MethodInvoker(delegate() { rtbIncoming.Text = reply; })); to just after the command is sent and it works!!!! about the handler name port_DataReceived_1 that is the only noncommented interrupt handler it was my name not Visual Studio's (great minds think alike ah no wait....) to fit in with others coding style (?) roll on Friday!! Thanks (how do I give you reputation points here?) Glenn

Vulpes · Answer

Hello Glenn As it was a question about the SerialPort I wondered whether it might be you ;) One thing that's worrying me about that code is the name of the handler: port_DataReceived_1 The _1 is usually a sign that a handler has been added twice by the VS designer. I'd check the Properties Box for the SerialPort component to see whether there are two handlers listed for the DataReceived event. If there are then the first handler may be grabbing the string leaving nothing in the buffer to be read by the second handler! That might explain why nothing is getting written to the richtextbox.

Glenn Patton · Answer

Hi Vulpes ex debugging.com hello. Umm tried a delegate in the event handler it didn't work and led to the issue see below: private void port_DataReceived_1(object senderSerialDataReceivedEventArgs e) { //int valueWait = WaitForData(12 10); InputData = myComPort.ReadExisting(); if (InputData != String.Empty) { this.BeginInvoke(new SetTextCallback(SetText) new object[]{ InputData}); } } Tried using the delegate you suggested with the same results! I am a little condfused.

Vulpes · Answer

If you're receiving the string in the SerialPort's DataReceived eventhandler and then assigning it to a textbox the problem may be that you're not marshalling the assignment back to the UI thread which is generally necessary when dealing with controls (it doesn't matter for MessageBox.Show). So instead of a line like this: rtbIncoming.Text = reply; I'd try code like this: this.Invoke(new MethodInvoker(delegate() { rtbIncoming.Text = reply; })); This assumes the DataReceived eventhandler is in your Form class - not a separate class.