unable to set statusstrip text from backgroundworker

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i have this code

Private Sub bwrkMain_ProgressChanged(ByVal sender As System.Object, _
           ByVal e As System.ComponentModel.ProgressChangedEventArgs) _
           Handles bwrkMain.ProgressChanged

    Dim strStatus As String = e.UserState.ToString
    Debug.Print(strStatus)
    Try
        Me.tsslStatus.Text = "status changed"
        lblStatus.Text = strStatus
    Catch ex As Exception
        MsgBox(ex.Message, MsgBoxStyle.Exclamation)
    End Try
End Sub

but the status text does not change, debug.print does print the message though.

i am calling the ReportProgress from another thread created by the backgroundworker thread.

is this the problem?

what could be causing this?

[edit]Inline code changed to code block - OriginalGriff[/edit]

Posted 19-Jun-11 0:15am

Cool Smith

Updated 19-Jun-11 0:18am

OriginalGriff

v2

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OriginalGriff · Accepted Answer · 2011-06-19T00:22:00

Solution 1

The problem is simple: you cannot access UI components except from the thread that created them - i.e. the UI thread.
When you try from another thread it doesn't work, and should throw an exception.

You need to PInvoke it:

Private Sub ShowProgress(text As String)
	If InvokeRequired Then
		Invoke(New MethodInvoker(Function() Do
			ShowProgress(text)
		End Function))
	Else
		Me.tsslStatus.Text = text
	End If
End Sub

"hell, am using .net 2.0, and this example doesn't work"

It's a bugger when that happens! :laugh:

Private Delegate Sub MyDelegate(text As String)
Private Sub ShowProgress(text As String)
	If InvokeRequired Then
		BeginInvoke(New MyDelegate(AddressOf ShowProgress), text)
	Else
		tsslStatus.Text = text
	End If
End Sub

Posted 19-Jun-11 0:22am

OriginalGriff

Updated 19-Jun-11 4:44am

v2

Comments

Simon_Whale 19-Jun-11 9:38am

great answer +5

Cool Smith 19-Jun-11 10:25am

hello, am using .net 2.0, and this example doesn't work

Cool Smith 19-Jun-11 11:08am

it was a typo, i wanted to say "hello, am using .net 2.0, and this example doesn't work"

OriginalGriff 19-Jun-11 11:14am

I guessed! :laugh:

BTW: for some reason comments aren't showing today - it's been reported, but it means this will only be visible in your email...

Sergey Alexandrovich Kryukov 19-Jun-11 23:06pm

Agree, all correct, my 5.
--SA

Cool Smith 23-Jun-11 4:03am

hello, i can't seem to call this from another form or module even when set to friend sub, why?

OriginalGriff 23-Jun-11 4:11am

Why would you want to?

Cool Smith 23-Jun-11 4:41am

i need to set the status from another function on outside the form

OriginalGriff 23-Jun-11 4:50am

Then you should create a property on the form which accepts the text, and uses the ShowProgress method to update the control: you shouldn't try to call it from outside the form directly. You need the form instance to access the property though - I am guessing that you aren't using it when you try to call the function directly?

Cool Smith 23-Jun-11 5:22am

i think i found the reason why the status will not set in the first places. when showing the form in question i do this

dim ofrm as new frmDialog
ofrm.ShowDialog(Me)

so in code am doing this

frmDialog.tsslStatus.Text = "Finding Submission Links..."

which i think is the reason it won't work

any solution around this

OriginalGriff 23-Jun-11 5:38am

No, that won't work - you need to refer to the instance of the form that holds status line you are interested in. It's like a car: you wouldn't expect top find you sunglasses in the glovebox of "a car": you will find them in the glovebox of "your car".
"A car" is the class (frmDialog), "your car" is the instance (ofrm in your example)

You should also be aware that the code will not continue executing after ShowDialog until the user closes the dialog (normally with OK or Cancel) - at which point he can't see the status line anyway... :laugh: