<Button x:Name="btnLocalOpc" Content="..."
      Grid.Column="1" HorizontalAlignment="Left"
      Command="{Binding PesquisarLocalServerCommand}"
      Margin="547,98,0,0" VerticalAlignment="Top"
      Width="43"  RenderTransformOrigin="0.5,0.5"/>

public ColectorsViewModel()
    {
        try
        {

            PesquisarLocalServerCommand = new Command(SearchLocalOpc);
            IsEditing = false;
            SelectedIndex = -1;
        }

    private void SearchLocalOpc()
    {
        using(OpcServerDialog serverDialog = new OpcServerDialog())
        {
            if(serverDialog.ShowDialog() == System.Windows.Forms.DialogResult.OK)
            {
              //capturo os dados aqui e preciso notificar a view
            }
        }
    }
        catch (Exception e)
        {
            throw e;
        }
    }