我不知道绑定源代码是什么，也不知道饼图LabelTemplate（转换器）是什么样的。我能提供的最多信息如下：

public class LabelTemplate : IValueConverter
{

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        //...
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        //...
    }
}
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        LabelTemplate labelTemplateConverter = new LabelTemplate();
        Binding binding = new Binding("Item.Items");
        binding.Converter = labelTemplateConverter;
        txtBlock.SetBinding(TextBlock.TextProperty, binding);
    }
}

和您的文本块的名称为txtBlock
我希望这能帮上忙。