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Background worker cancelling from another form

Posted on 2016-09-23
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Last Modified: 2016-10-09
Using vb.net for an application i'm developing.  During a backgroundworker routine, I have a semi-transparent overlay form over top with a progress bar and cancel button.  However when I try to cancel I get the error: Object reference not set to an instance of an object.

How can I cancel a backgroundworker from another form?  This is my code from the second (overlay) form.

Public Class CISMapOverlay
     Private myParent As frmGMapNet

    Private Sub Label2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles RadLabel2.Click
        Me.myParent.BackgroundWorker1.CancelAsync()
        Me.Hide()
    End Sub

    Public Sub New()

        ' This call is required by the designer.
        InitializeComponent()
        Me.myParent = myParent

        ' Add any initialization after the InitializeComponent() call.

    End Sub
End Class

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Question by:K-9
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AndyAinscow earned 500 total points
ID: 41812492
You never assign a value to your variable myParent in the code you show.  Once you set that to the 'parent' form you should be able to do what you want (BackgroundWorker1 would need to be a public variable).
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Author Comment

by:K-9
ID: 41812493
Yes I did: Private myParent As frmGMapNet
frmGMapNew is the form where the Backgroundworker is.
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Author Comment

by:K-9
ID: 41812502
Wow.. that's weird.  If I use frmGMapNew.BackgroundWorker1.CancelAsync() it works.  For some reason it doesn't like using myParent
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LVL 44

Expert Comment

by:AndyAinscow
ID: 41812534
Sounds like you have the BackgroundWorker1 as a static variable in that case.
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Expert Comment

by:AndyAinscow
ID: 41812537
ps.  I told you why the myParent doesn't work in my first comment.
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LVL 44

Expert Comment

by:AndyAinscow
ID: 41828034
My first comment points out what is wrong with the code supplied and how to fix it.
#a41812492
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