[Solved] Threading error

[griggle]

Hi, I am using phidget device to collect information from the sensor. However, whenever I run the program, this error shows up, saying that "The calling thread cannot access the object because a different thread owns it"

The code:

Private Sub phid_SensorChange(ByVal sender As Object, ByVal e As Phidgets.Events.SensorChangeEventArgs) Handles phid.SensorChange
If e.Index = 0 Then
lblDisplayTemp.Content = e.Value.ToString
End If

End Sub

How do I solve this problem?

[jmcilhinney]

You cannot access most control members directly from a thread other than the one on which its handle was created. In most apps the "main thread" or "UI thread" is the one on which your app was started and the one that creates all your forms and, therefore, all your controls. As such, you can only access most control properties on that main thread.

Before I go any further, I see that you are accessing the Content property of what appears to be a Label. That would suggest that you're using WPF rather than WinForms. Is that the case? If so then this site has a forum dedicated to WPF that be a more appropriate place for this thread. Let us know if it is WPF and we can get the mods to move the thread. The way to handle this situation is most likely different in WPF than WinForms.

[griggle]

To jmcilhinney: Yes, I am using WPF.

[jmcilhinney]

Just had a quick search:

http://www.google.com.au/search?q=cr...ient=firefox-a

http://anoriginalidea.wordpress.com/...dating-in-wpf/

Based on my knowledge of this situation in WinForms and that information, I just tried this and it worked:

Class Window1
 
    Private WithEvents clock As New Timers.Timer With {.Interval = 5000, .Enabled = True, .AutoReset = False}
 
    Private Sub clock_Elapsed(ByVal sender As Object, ByVal e As System.Timers.ElapsedEventArgs) Handles clock.Elapsed
        Me.SetLabelContent("Hello World")
    End Sub
 
    Private Sub SetLabelContent(ByVal content As Object)
        If Me.Label1.Dispatcher.Thread Is System.Threading.Thread.CurrentThread Then
            Me.Label1.Content = content
        Else
            Me.Label1.Dispatcher.Invoke(New Action(Of Object)(AddressOf SetLabelContent), content)
        End If
    End Sub
 
End Class

You can follow the CodeBank link in my signature and check out my Accessing Controls From Worker Threads post to see how to create code like this. As you should be able to see, the difference is minor between WinForms and WPF.

[griggle]

Problem solved.