How to create custom legend items in WPF Chart?

<DataTemplate x:Key="itemTemplate"> 
        <StackPanel Margin="10,0,10,0"  Orientation="Horizontal"> 
                    <CheckBox Margin="2" Tag="{Binding}" 
                              IsChecked="True" 
                              Checked="CheckBox_Checked"   
                              Unchecked="CheckBox_Unchecked"/> 
 
                    <Rectangle  Width="{Binding IconWidth}"  
                                Height="{Binding IconHeight}"                                         
                                Fill="{Binding Interior}" Margin="2"/> 
 
                    <TextBlock HorizontalAlignment="Center" 
                               Margin="5,0,0,0" 
                               VerticalAlignment="Center" 
                               Text="{Binding Item.XValue}"> 
 
                    </TextBlock> 
          </StackPanel> 
</DataTemplate> 

          ChartLegend legend = new ChartLegend(); 
 
            foreach (var series in chart.Series) 
            { 
                var data = series.ItemsSource as ObservableCollection<Model>; 
                for (int i = 0; i < data.Count; i++) 
                { 
                    legend.Items.Add(new LegendItem() 
                    { 
                        Item = data[i].XValue.ToString(), 
                        Series = series, 
                        IconHeight = 10, 
                        IconWidth = 10, 
                        IconVisibility = Visibility.Visible, 
                        Interior = series1.ColorModel.GetBrush(i),
                        CheckBoxVisibility = Visibility.Visible
                    }); 
                } 
            } 
 
            legend.ItemTemplate = grid.Resources["itemTemplate"] as DataTemplate; 
            chart.Legend = legend; 

        private void CheckBox_Checked(object sender, RoutedEventArgs e) 
        { 
            CheckBox box = sender as CheckBox; 
            LegendItem item = box.Tag as LegendItem; 
 
            UpdateLegend(true, item.Item as Model); 
        } 
 
        private void CheckBox_Unchecked(object sender, RoutedEventArgs e) 
        { 
            CheckBox box = sender as CheckBox; 
            LegendItem item = box.Tag as LegendItem; 
 
            UpdateLegend(false, item.Item as Model); 
        } 
 
        private void UpdateLegend(bool isChecked, Model item) 
        { 
            foreach (PieSeriesExt series in chart.Series) 
            { 
                if (isChecked) 
                    toggleIndexes.Remove(viewModel.Data.IndexOf(item)); 
                else 
                    toggleIndexes.Add(viewModel.Data.IndexOf(item)); 
 
                series.GetType().GetField("ToggledLegendIndex", BindingFlags.NonPublic | 
                    BindingFlags.Instance).SetValue(series, toggleIndexes); 
            } 
 
            UpdateArea(); 
        } 
 
        private void UpdateArea() 
        { 
            MethodInfo info = chart.GetType().GetMethod("UpdateArea", 
                               BindingFlags.NonPublic | BindingFlags.Instance, 
                               null, 
                               new Type[] { typeof(bool) }, 
                               null); 
 
            info?.Invoke(chart, new object[] { true }); 
        }