DataGridComboBoxColumn binding using SelectedValueBinding and SelectedValuePath

Question

I have been working on dummy project to understand binding in DataGridComboBoxColumn and in that I have encountered to SelectedValuePath and SelectedValue Binding.

I have looked up to various source of other questions too to understand such as:

• C# WPF - Databinding DataGridComboboxColumn SelectedValueBinding
• Confused with wpf ComboBox DisplayMemberPath,SelectedValue and SelectedValuePath
• Difference between SelectedItem, SelectedValue and SelectedValuePath

The problem in my code is it gets bound with SelectedItemBinding, but not with SelectedValuePath & SelectedValueBinding.

using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Windows;
using System.Windows.Controls;

namespace WpfApplication10
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            DataContext = new MainViewModel();
        }
    }

    public class Item
    {
        public int ID { get; set; }
        public string Name { get; set; }
        public string Code { get; set; }

        // Property for the composite value
        public string CombinedValue => $"{ID}_{Name}_{Code}";
    }

    public class MainViewModel : INotifyPropertyChanged
    {

        public event PropertyChangedEventHandler PropertyChanged;

        private void OnPropertyChanged(string propertyName)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }

        private Item _selectedItem;

        public Item SelectedItem
        {
            get { return _selectedItem; }
            set
            {
                if (_selectedItem != value)
                {
                    _selectedItem = value;
                    OnPropertyChanged(nameof(SelectedItem));
                }
            }
        }

        public ObservableCollection<Item> Items { get; set; }

        public ObservableCollection<string> Codes { get; set; }

        public MainViewModel()
        {
            Items = new ObservableCollection<Item>
            {
                new Item { ID = 1, Name = "Item 1", Code = "A" },
                new Item { ID = 2, Name = "Item 2", Code = "Z" },
                new Item { ID = 3, Name = "Item 3", Code = "C" },
                new Item { ID = 4, Name = "Item 4", Code = "A C" }
            };

            Codes = new ObservableCollection<string>(Items.Select(item => item.Code).Distinct());
            SelectedItem = Items.FirstOrDefault();
        }
    }
}

I have tried below with SelectedItemBinding and it works

<DataGridComboBoxColumn Header="Code" SelectedItemBinding="{Binding Code}" Width="100" IsReadOnly="True">
    <DataGridComboBoxColumn.ElementStyle>
        <Style TargetType="ComboBox">
            <Setter Property="ItemsSource" Value="{Binding DataContext.Codes, 
                RelativeSource={RelativeSource AncestorType=Window}}"/>
        </Style>
    </DataGridComboBoxColumn.ElementStyle>
    
</DataGridComboBoxColumn>

I want to implement above with SelectedValueBinding & SelectedValuePath.

I have tried this till now

<DataGridComboBoxColumn Header="Value-Binded" ItemsSource="{Binding DataContext.Items}"
                        SelectedValuePath="Code"
                        SelectedValueBinding="{Binding ID , UpdateSourceTrigger=PropertyChanged}"
                        >                   
</DataGridComboBoxColumn>

DataGrid defined as

<DataGrid ItemsSource="{Binding Items}" AutoGenerateColumns="False" CanUserAddRows="False">

And DataContext as

<Window.DataContext>
    <local:MainViewModel/>
</Window.DataContext>