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Multi-threading

I tried to write an windows application using my .dll file. I created a library MyLibrary in which I implemented a class called Scanner. In the Scanner class, I had a method called Scanning which used a method from another .dll file to scan the driver license. In the Scanner class, I also had another method called MyThread which created a thread with the starting entry is Scanner (New Thread(AddressOf Me.Scanner)). Also, I created a windows application with a form and a button. I import MyLibrary into this windows application. When I click the button on the form to scan the driver license, the scanner scanned the driver license, but I could not interact with the form to type something in during the time the scanner scanned the driver license. After it finished scanning, then I could interact with the form. Is there anyway that I can interact with the form during the time the scanner scans the driver license? Please help me out and it would be nice if I can see the sample code. Thanks.

KeirGordon

It is hard to help without seeing some of your code, but typically to solve an issue such as this one would insert Application.DoEvents() calls within any loops they have. This call allows any pending messages to be proccessed and thus will often fix the issue of your form not responding while in a loop.

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gregoryyoung

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gregoryyoung

oops forgot when the thread dies to set it to nothing (so isRunning still works ...)

gregoryyoung

also I believe its Stop() on the thread not abort()

http://www.dotnetbips.com/displayarticle.aspx?id=39 is a decent itro to threading reference
Also MSDN has a ton of good examples if you look in the threading area :)

UiTroi

ASKER

This is not quite what I need, but it gives me the direction. The problem was that when I was scanning, all theads were blocked. I think that it is the problem of ActiveX control. Anyway, thanks a lot for your time and your help.

gregoryyoung

the code above handles that case by starting a thread (which gets blocked) and calling back to your other thread (which is still alive) when the image completed scanning ...

gregoryyoung

this creates a thread and returns to your main thread.
Public Sub Scanning()
//lock this
SingleScanThread=new Thread
(new ThreadStart(addressof Me.GetMyImage))
//unlock this
End Sub

this runs in the new thread
Protected Sub GetMyImage()
try
//this calls your activex control
dim img as Image = OtherLibrary.DoScan()

//this messages your first thread which has been processing other tasks that the image has been completed (and delivers the image to the first thread)
OnScanCompleted(img)
catch Ex as ThreadException
'Thread was cancelled
catch Ex as Exception
'Raise most likely another event which would alert the user to the other error
end try
End Sub