How to safely access a global variable from a backgroundworker thread vb.net

Question

I've got a backgroundworker implemented in my program and it's accessing a global variable decalred outside the thread. IT causes no errors but setting the checkillegalstring property and there are cross thread exceptions all over the place. I found out that it's because it's using the global variable I've declared previously.

I can't seem to find anywhere that I can use a global variable inside my backgroundworker thread, is this possible to do?

The best solution will depend on how you use that variable. Can you post some of the code? — Joel Coehoorn, Jul 30 '13 at 21:21

Kevin DiTraglia · Accepted Answer · 2013-07-30T21:21:41.107

4

The simplest way is with SyncLock

Sub firstNewThread()
    SyncLock objLock
        'Access global object
    End SyncLock
End Sub
Sub secondNewThread()
    SyncLock objLock
        'Guaranteed to not be executing while block in first thread is running
    End SyncLock
End Sub

Just be aware of other pitfalls like deadlocks that may occur from this.

edited Jul 30 '13 at 21:21

answered Jul 30 '13 at 21:16

Kevin DiTraglia

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Thanks! I'm just looking to read the data, no updating will be occuring on the form. – Criel Jul 30 '13 at 21:16

score 3 · Answer 2 · edited May 23 '17 at 10:31

3

Perhaps you can try SyncLock.

See this answer: https://stackoverflow.com/a/915877/153923

For example:

// C#
lock (someLock)
{
    list.Add(someItem);
}

// VB
SyncLock someLock
    list.Add(someItem)
End SyncLock

edited May 23 '17 at 10:31

Community

1
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answered Jul 30 '13 at 21:16

How to safely access a global variable from a backgroundworker thread vb.net

2 Answers2