<ListBox.ItemTemplate>
                <DataTemplate>
                    <Grid Margin="3">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition></ColumnDefinition>
                            <ColumnDefinition Width="auto"></ColumnDefinition>
                        </Grid.ColumnDefinitions>
                            <StackPanel Orientation="Horizontal" Grid.Column="0" >
                            <TextBlock Text="{Binding Path=FName_}" Tag="{Binding Path=LName_}"/>
                            <TextBlock Text=" "/>
                            <TextBlock Text="{Binding Path=LName_}"/>
                        </StackPanel>
                        <Button Grid.Column="1" Click="Button2_Click" Tag="{Binding Path=FName_}" Content="Detalis" Width="auto"></Button>
                    </Grid>
                  
                </DataTemplate>
            </ListBox.ItemTemplate>

 Dim tn As Button = CType(sender, Button)
 Dim sa As String = CType(tn.Tag, String)

Private Sub cmbCountry_SelectionChanged(sender As System.Object, e As System.Windows.Controls.SelectionChangedEventArgs) Handles cmbCountry.SelectionChanged
        Dim s As String = CType(CType(sender, ComboBox).SelectedItem, TRefService.Country).Name_
End Sub