run multiple BackgroundWorkers with single DoWork sub

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Hello,

how do i run multiple BackgroundWorkers with single DoWork and progresschanged sub?
for example, somthing like

dim ListOfTask as new list(Of string)

TestWorker1 = New System.ComponentModel.BackgroundWorker
TestWorker2 = New System.ComponentModel.BackgroundWorker
AddHandler TestWorker1.DoWork, AddressOf TestWorker_DoWork
AddHandler TestWorker2.DoWork, AddressOf TestWorker_DoWork

private sub TestWorker_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs)
if listoftask.count >1 then
'// do the work with a new worker
end if
end sub

will this work?

Posted 31-May-11 6:11am

Cool Smith

Updated 31-May-11 7:36am

v3

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Sergey Alexandrovich Kryukov · Accepted Answer · 2011-05-31T06:34:00

Solution 1

Running the same method in two separate thread is no different from running two different methods in two different threads. You will clearly see it if you consider how threads work.

It all depends on how this methods is written. The same precautions to thread synchronization apply, such as synchronization of access to any shared resources. The same very threading hazards may occur, such as deadlocks (http://en.wikipedia.org/wiki/Deadlock[^]) or race conditions (http://en.wikipedia.org/wiki/Race_condition[^]).

[EDIT — per our discussion]
This is a collection of my past answer on the topic:
How to get a keydown event to operate on a different thread in vb.net[^],
Control events not firing after enable disable + multithreading[^].

Pay attention for the thread wrapper technique, very important and convenient:
How to pass ref parameter to the thread[^].
Translated to VB.NET by VSNetVbHarry:
Passing arguments to a threaded LongRunningProcess[^].

—SA

Posted 31-May-11 6:34am

Sergey Alexandrovich Kryukov

Updated 2-Jun-11 7:40am

v3

Comments

Cool Smith 31-May-11 12:43pm

each worker will have to work with a different variable

Sergey Alexandrovich Kryukov 31-May-11 19:10pm

No! Who tells you so? Not true. What variable?
They can work with shared data, separate data, whatever required. It's only important to do proper synchronization.
--SA

Sergey Alexandrovich Kryukov 6-Jun-11 12:07pm

At the same time I think I understand what do you mean. Each thread works with its own version of data. Right. That's why I reference a thread wrapper. The individual storage for data will be per instance of the wrapper. You have one instance of the wrapper per instance of the thread, so you will not share individual thread's data.
--SA

Cool Smith 2-Jun-11 13:00pm

can you help me with a sample code that uses background workers?

Sergey Alexandrovich Kryukov 2-Jun-11 13:36pm

What kind? How about original Microsoft sample on MSDN page:
http://msdn.microsoft.com/en-us/library/system.componentmodel.backgroundworker.aspx

Why background worker? In many cases an explicitly created thread is better. Please explain your ultimate goals, if you have those.
I have a lot of matter on threading here at CodeProject, will give you a collection in links to my past answer. You will learn what's involved and then ask you questions.
If you pose a new question (create a separate page), that would be fine, but don't forget to notify me by replying to this comment, use "Reply" on top right.
--SA

Cool Smith 6-Jun-11 3:39am

hello, i posted the problem here http://www.codeproject.com/Questions/206689/Multiple-backgroundworkers-problem

Sergey Alexandrovich Kryukov 6-Jun-11 12:04pm

I think you got a solution. Or you did not? Then comment about it, ask a follow-up question.

Do you have a solution for this problem? You ask a sample, and I gave you one, that's all.
I feel the problem is different. First, I don't quite understand how you improve the throughput running the same task in parallel. I guess you run the same task with different parameters; and the each task does not depend on results of others. In this case you can improve throughput, but you never need more threads then the number of cores. You can also gain by using new Task library instead of threads. Also, I'm not sure background worker is good enough. You may better need regular threads created under the wrapper you find in my links. Look at Tasks though.
--SA

Cool Smith 6-Jun-11 16:01pm

when one is using multiple threads, is it possible to process more that one job at once, using the same work sub without having the risk of change values when one thread has not finished using it?

Sergey Alexandrovich Kryukov 6-Jun-11 20:16pm

Yes ****of course**** if you manage and separate data properly. My thread wrapper is one of the ways, a good one. Any questions?
--SA