Updating UI from another thread with VB in WPF

Question

I am trying to use a timer to scan my Xbox 360 controller. But I cannot directly update my UI like the code I wrote below.

I would get a exception when I try to run this code.

An exception of type 'System.InvalidOperationException' occurred in WindowsBase.dll but was not handled in user code

Additional information: The calling thread cannot access this object because a different thread owns it.

XButton is a radiobutton on the GUI that I want to toggle.

Imports Microsoft.Xna.Framework
Imports Microsoft.Xna.Framework.Input
Imports System.Timers
Imports System.Windows.Threading

Public Class XboxControllerStatus
Friend WithEvents Timer1 As Timer


Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Elapsed

    Dim currentState As GamePadState = GamePad.GetState(PlayerIndex.One)
    If currentState.IsConnected Then
        If currentState.Buttons.X.Pressed Then
            XButton.IsChecked = True

        Else
            XButton.IsChecked = False

        End If
    End If

End Sub

End Class

Ikechi Michael · Accepted Answer · 2015-10-02 09:55:38Z

3

This works for me, all the time

Control.Invoke(sub()
                  'Put code here
               End Sub)

answered Oct 2, 2015 at 9:55

Ikechi Michael

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1 Comment

Lorne K Over a year ago

This is a very good answer - not sure why it's buried with no upvotes

Rob · Accepted Answer · 2015-10-02 02:36:46Z

0

First you need to set up a delegate

Delegate Sub SetCheckBoxCallback(ByVal value As Boolean)
Friend Sub SetCheckBox(ByVal value As Boolean)
    XButton.IsChecked = value
End Sub

after that all you need to do is call the following code from within your timer to invoke it:

Dim DesiredValue as Boolean = True

Me.Dispatcher.Invoke(New SetCheckboxCallback(AddressOf SetCheckbox), New Object() {DesiredValue})

answered Oct 2, 2015 at 2:36

Rob

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