<Grid x:Name="LayoutRoot" Background="White">
        <data:DataGrid Name="dataGrid1" AutoGenerateColumns="False">
            <data:DataGrid.Columns>
                <data:DataGridTextColumn Header="Bumper" Binding="{Binding Path=Bumper.Value}"></data:DataGridTextColumn>
                <data:DataGridTextColumn Header="Wheel" Binding="{Binding Path=Wheel.Value}"></data:DataGridTextColumn>
                <data:DataGridTemplateColumn>
                    <data:DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <ComboBox .....???..... />
                        </DataTemplate>
                    </data:DataGridTemplateColumn.CellTemplate>
                </data:DataGridTemplateColumn>
            </data:DataGrid.Columns>
        </data:DataGrid>
    </Grid>

namespace Silver
{
    public partial class MainPage : UserControl
    {
        public class Element
        {
            public int ID { get; set; }
            public string Value { get; set; }

            public Element() { }

            public Element(int ID, string Value)
            {
                this.ID = ID;
                this.Value = Value;
            }
        }

        public class Cars
        {
            public Element Wheel { get; set; }
            public Element Bumper { get; set; }
            public List<Element> Color { get; set; }
        }

        public MainPage()
        {
            InitializeComponent();

            List<Element> color = new List<Element>()
            {
                new Element( 1 , "Red"),
                new Element( 2 , "Orange"),
                new Element( 3 , "Yellow")
            };
            List<Cars> Cars = new List<Cars>()
            {
                new Cars() { Bumper = new Element( 1 , "Tayota"), Wheel = new Element( 1 , "Mishlen"), Color = color},
                new Cars() { Bumper = new Element( 10 , "Bmw"), Wheel = new Element( 11 , "Gradiant"), Color = color},
                new Cars() { Bumper = new Element( 20 , "Mercedes"), Wheel = new Element( 22 , "Mishlen3"), Color = color}
            };

            dataGrid1.ItemsSource = Cars;
        }
    }
}