WPF DataGridComboBoxColumn与ICollection子类别的绑定

Question

类别：类别 我们正在尝试将ICollection子类别（成员：Category1）与数据网格的组合框列绑定。

public partial class Category
{
    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
    public Category()
    {
        this.Category1 = new HashSet<Category>();
    }

    public long CategoryID { get; set; }
    public string CategoryName { get; set; }
    public Nullable<long> ParentID { get; set; }
    public Nullable<int> Status { get; set; }

    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
    public virtual ICollection<Category> Category1 { get; set; }
    public virtual Category Category2 { get; set; }
}

XAML代码：

    public CategoryPage()
    {
        InitializeComponent();
        bindCategoriesWithDataGrid();
    }
    private void bindCategoriesWithDataGrid()
    {
        entities = new RestaurantDatabaseEntities();
        dgridCategories.ItemsSource = entities.Categories.ToList();
    }

XAML UI：

<DataGrid AutoGenerateColumns="False" Height="226" Grid.Row="0" Grid.Column="1"
      HorizontalAlignment="Left" Margin="10,10,0,0"
      Name="dgridCategories" VerticalAlignment="Top" Width="684" ColumnWidth="*"
      RowEditEnding="dgCategory_RowEditEnding"  CellEditEnding="dgCategory_CellEditEnding"
      SelectionChanged="dgCategory_SelectionChanged" >
            <DataGrid.Columns>
                <DataGridTextColumn Binding="{Binding CategoryName}" Header="Category Name"
                  IsReadOnly="True" x:Name="dgrCategoryName">
                </DataGridTextColumn>
                <DataGridComboBoxColumn Header="Sub Category" ItemsSource="{Binding Category1}"
                                        DisplayMemberPath="CategoryName"
                                        x:Name="dgrSubCategories"/>

这不起作用，并且在数据网格中显示了空的组合框。