How do I update a Listbox in realtime
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I've got a VB.Net windows program that monitors a database This progam sits in a repetitive loop. I would like to be able to output some data about what the program, had been doing in each loop. The problem is that the listbox on the user interface does not display anything until the process has eneded. Does any onw know how I do this?
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I've got a VB.Net windows program that monitors a database This progam sits in a repetitive loop. I would like to be able to output some data about what the program, had been doing in each loop. The problem is that the listbox on the user interface does not display anything until the process has eneded. Does any onw know how I do this?
Martijn Groen wrote:
The problem is that the listbox on the user interface does not display anything until the process has eneded.
Looks like you have only a single thread. Try to run the operation on a different thread. If you are adding items continuosly in a tight loop, use ListBox.BeginUpdate()[^] and once finished call ListBox.EndUpdate()[^]. This will prevent unnecessary drawing the listbox.
Navaneeth How to use google | Ask smart questions
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Martijn Groen wrote:
The problem is that the listbox on the user interface does not display anything until the process has eneded.
Looks like you have only a single thread. Try to run the operation on a different thread. If you are adding items continuosly in a tight loop, use ListBox.BeginUpdate()[^] and once finished call ListBox.EndUpdate()[^]. This will prevent unnecessary drawing the listbox.
Navaneeth How to use google | Ask smart questions
Thanks Navaneeth I've tried using the update. It doesn't seem to do what I'm trying to achieve. What I need is to be able to update the listbox realtime eg to show data flowing through (mid loop) rather then render the control with all data when the sub completed execution. I want to build a data flow monitoring tool that sites on a desktop. For the below code I'm aiming forthe application to pump a new item into the listbox visually in every iteration of the loop. I've added the thread sleep to slow it down and spread the timestamp apart. Dim counter As Integer = Nothing Do While counter < 100 counter += 1 ListBox1.Items.Add(" timestamp output " & Now) Threading.Thread.Sleep(200) Loop Does anyone have any ideas?
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Thanks Navaneeth I've tried using the update. It doesn't seem to do what I'm trying to achieve. What I need is to be able to update the listbox realtime eg to show data flowing through (mid loop) rather then render the control with all data when the sub completed execution. I want to build a data flow monitoring tool that sites on a desktop. For the below code I'm aiming forthe application to pump a new item into the listbox visually in every iteration of the loop. I've added the thread sleep to slow it down and spread the timestamp apart. Dim counter As Integer = Nothing Do While counter < 100 counter += 1 ListBox1.Items.Add(" timestamp output " & Now) Threading.Thread.Sleep(200) Loop Does anyone have any ideas?
Again, you have to move the code that is generating the data to a new thread, then Invoke a method on the form to update the ListBox on the UI thread. Don't worry about the BeginUpdate and Endupdate methods just yet. Worry about getting the data to the control from a background thread first. You may want to look into the BackgroundWorker component if doing your own threading is a bit intimidating.
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Thanks Navaneeth I've tried using the update. It doesn't seem to do what I'm trying to achieve. What I need is to be able to update the listbox realtime eg to show data flowing through (mid loop) rather then render the control with all data when the sub completed execution. I want to build a data flow monitoring tool that sites on a desktop. For the below code I'm aiming forthe application to pump a new item into the listbox visually in every iteration of the loop. I've added the thread sleep to slow it down and spread the timestamp apart. Dim counter As Integer = Nothing Do While counter < 100 counter += 1 ListBox1.Items.Add(" timestamp output " & Now) Threading.Thread.Sleep(200) Loop Does anyone have any ideas?
Hi, as others have said, you need a separate thread to keep things running AND your GUI alive. Choose one of Thread, ThreadPool, or BackgroundWorker. The former is the most flexible, the latter often is the most comfortable. You could implement a loop in its DoWork handler, include a Thread.Sleep if you want to, and call ReportProgress() to report progress on the GUI; i.e. your Progress handler could add data to the ListBox. That would seem the easiest way to avoid cross-thread problems. And you might want to read this little article[^] if you would consider another way (Thread, ThreadPool; or even BackgroundWorker without ReportProgress). :)
Luc Pattyn [Forum Guidelines] [My Articles]
The quality and detail of your question reflects on the effectiveness of the help you are likely to get. Show formatted code inside PRE tags, and give clear symptoms when describing a problem.
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Hi, as others have said, you need a separate thread to keep things running AND your GUI alive. Choose one of Thread, ThreadPool, or BackgroundWorker. The former is the most flexible, the latter often is the most comfortable. You could implement a loop in its DoWork handler, include a Thread.Sleep if you want to, and call ReportProgress() to report progress on the GUI; i.e. your Progress handler could add data to the ListBox. That would seem the easiest way to avoid cross-thread problems. And you might want to read this little article[^] if you would consider another way (Thread, ThreadPool; or even BackgroundWorker without ReportProgress). :)
Luc Pattyn [Forum Guidelines] [My Articles]
The quality and detail of your question reflects on the effectiveness of the help you are likely to get. Show formatted code inside PRE tags, and give clear symptoms when describing a problem.
Thanks to everyone for their feedback I've got it going now ;)