asked on

Threading with a function returning value to windows form control

Hi all,
I'm trying to create a thread that passes parameters into a function. the return value needs to be set to a label control. I'm having a problem figuring out how to do this.

the function looks like this:
lblFILESIZE.Text = CONVERT_FILESIZE(GET_FILESIZE(txtSOURCE.Text, COPY_TYPE$), False)

any help would be greatly appreciated.
thanks,
John.

ASKER CERTIFIED SOLUTION

Luis Pérez

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CodeJunky

ASKER

could you provide an example?

Luis Pérez

Imports System.Threading

'At form level:
Private _myThread As Thread = Nothing
Private _myVariable As String = String.Empty

'When you want to start your thread
_myThread = New Thread(AddressOf MiThreadSub)
_myThread.Start()
'Monitorize thread
While _myThread.IsAlive()
    Application.DoEvents() 'Or, better, check for your thread alive status into a timer
End While
'Once outside of the while...end while, your thread has finished
'Now you can check your _myVariable status and put it into a label or wherever you want
Me.Label1.Text = _myVariable

'What your thread does:
Private Sub MiThreadSub()
    '... do something
    'If the thread is executing inside a Windows Form, you cannot access Form objects
    'such as labels, etc.
    'But you can store values into form variables
    'For example:
    _myVariable = "Hello"
End Sub

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Note that this code doesn't work if you simply paste it into a Form. For example, the "When you want to start your thread" block needs to be written somewhere it can execute, for example, a button's click event.

Hope that helps.

CodeJunky

ASKER

I figured it out.
I created a backgroundworker object
I created a variable to hold the result from the function within the backgroundworker .DoWork procedure.
I created a backgroundworker .RunWorkerCompleted procedure where I set that variable to the object it is meant for.

thanks,
John.