列表框选择事件错误

Question

我使用列表框选择从列表框中选择一个项目，但我选择它，它产生了一个卑劣的exception.Here我的代码是： `

<ListBox Grid.Row="1" SelectionChanged="PrintText" Background="DarkGray" Visibility="Collapsed" Height="Auto" HorizontalAlignment="Left" Margin="156,36,0,0" Name="listBox1" VerticalAlignment="Top" Width="191" UseLayoutRounding="True" /> 

void PrintText(object sender, SelectionChangedEventArgs args) 
     { 
      ListBoxItem lbi = ((sender as ListBox).SelectedItem as ListBoxItem); 
      String a = lbi.Content.ToString(); 
      Window1 neww = null; 
      neww = new Window1(); 
      neww.Show(); 
     } 

`我不不知道我在哪做错误请引导我。我附上了它的图像，让你更清楚。 谢谢！

Answer 1

void PrintText(object sender, SelectionChangedEventArgs args) 
{ 
    object item = listBox1.SelectedItem; 

    if (item == null) { 
    txtSelectedItem.Text = "No item currently selected."; 
    } else { 
    txtSelectedItem.Text = item.ToString(); 
    } 

    // ListBoxItem lbi = ((sender as ListBox).SelectedItem as ListBoxItem); 
    // String a = lbi.Content.ToString(); 
    Window1 neww = null; 
    neww = new Window1(); 
    neww.Show(); 
}