如后面的加号，选中行时出现，未被选中的隐藏

解决：

在按钮中的visibility属性中绑定该item是否选中，再用转换器转换

<Button Name="btnA" Click="btnA_Click_1" BorderBrush="Transparent" BorderThickness="0" Background="Transparent" Visibility="{Binding RelativeSource={RelativeSource AncestorType=ListViewItem}, Path=IsSelected,Converter={StaticResource btnshowConverter}}">+</Button>

public class btnshowConverter : IValueConverter
 {
       public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
      {
             if (value.ToString() == "True") return "Visible";
             if (value.ToString() == "False") return "Collapsed";
             return value;
      }
      public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
     {
             throw new NotImplementedException();
     }
}