CODEWITHSUNDEEP
c#wpfvb.net
iAteABug_And_iLiked_it
iAteABug_And_iLiked_it

Reputation: 3795

How to use InvokeRequired

I have the code below in vb.net, and I am converting it to c#. EDIT Edited out irrelevant code.

but I am stuck at the one with InvokeRequired. I have added a reference to System.Windows.Forms and still the code completion doesn't show InvokeRequired. The listview is on a separate thread to the one I am calling it from, and I need to get around that using Invoke. Can you please tell me what am I missing? Thank you.

    Delegate Sub _AddClient(ByVal client As Socket)
    Private Sub AddClient(ByVal client As Socket)
        If InvokeRequired Then
            Invoke(New _AddClient(AddressOf AddClient), client)
            Exit Sub
        End If
        Dim lvi As New ListViewItem(client.LocalEndPoint.ToString)
        lvi.Tag = client
        lsvClients.Items.Add(lvi)
    End Sub

Upvotes: 1

Views: 7957

Answers (3)

Fede
Fede

Reputation: 44048

Dude, if you're working with WPF, remove all references to System.Windows.Forms, WPF doesn't need, nor care about that, and you'd better not be confused with classes with equal names from different namespaces and frameworks (for instance System.Windows.Forms.Control and System.Windows.Control.

InvokeRequired() does not exist in WPF, that's replaced by Dispatcher.CheckAccess().

Upvotes: 2

Hanlet Escaño
Hanlet Escaño

Reputation: 17380

Try this:

Delegate Sub _AddClient(ByVal client As Socket)
Private Sub AddClient(ByVal client As Socket)
    If ListView1.InvokeRequired Then
        Invoke(New _AddClient(AddressOf AddClient), client)
        Exit Sub
    End If
    Dim lvi As New ListViewItem(client.LocalEndPoint.ToString)
    lvi.Tag = client
    ListView1.Items.Add(lvi)
End Sub

Upvotes: 1

Pieter Geerkens
Pieter Geerkens

Reputation: 11893

Here is an example of how it is used:

protected void InvokePathDone(Task<IPath<ICoordsCanon>> task,
                              Action<Task<IPath<ICoordsCanon>>> action) {
  if (InvokeRequired)  Invoke(action, task);
  else                 action(task);
}

Update for OP question below:

InvokeRequired() is defined for the Control class to enable callbacks from event delegates to determine if they are, or are not, on the UI thread, and thus whether they must, or must not, perform their action under Invoke().

Upvotes: 0

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