GridViewComboBoxColumn doesn't drop down and show values for edit.

[Brady]

I have the following two classes:
public class Gender

{
    public int Id { get; set; }
    public string Name { get; set; }
}

public class Person
{
    public string Name { get; set; }
    public int? GenderId { get; set; }
    public bool IsActive { get; set; }
}

And I have the following RadGridView, bound to an ObservableCollection<Person>, wanting to use a ComboBox to choose their gender:

<telerik1:RadGridView x:Name="Grid"                              
                        ItemsSource="{Binding Persons}"
                        IsSynchronizedWithCurrentItem="True"
                        AutoGenerateColumns="False" 
                        ShowGroupPanel="False" 
                        ShowInsertRow="True"
                        CanUserInsertRows="true">
    <telerik1:RadGridView.Columns>
        <telerik1:GridViewDataColumn Header="Name" DataMemberBinding="{Binding Name}" Width="*" />
        <telerik1:GridViewComboBoxColumn
                Name="Gender"
                Header="Gender"  
                DataMemberBinding="{Binding GenderId}"
                DisplayMemberPath="Name"
                SelectedValueMemberPath="Id"
                ItemsSourceBinding="{Binding Genders}"
                EditTriggers="CellClick"
                IsReadOnly="False"
                Width="80"  />
        <telerik1:GridViewCheckBoxColumn
            DataMemberBinding="{Binding IsActive}"
            Header="Active"
            IsReadOnly="False" />
    </telerik1:RadGridView.Columns>
</telerik1:RadGridView>

I followed one of Telerik's examples I found somewhere to define the Combo column, and it has values

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();
        DataContext = this;
 
        Genders = new ObservableCollection<Gender>
            {
                new Gender {Id = 0, Name = "Female"},
                new Gender {Id = 1, Name = "Male"},
                new Gender {Id = 2, Name = "Withheld"}
            };
 
        Persons = new ObservableCollection<Person>
            {
                new Person {Name = "Andy", GenderId = 1, IsActive = false},
                new Person {Name = "Mary", GenderId = 0, IsActive = true},
                new Person {Name = "Peta", GenderId = 2, IsActive = true},
                new Person {Name = "Gerald", GenderId = 0, IsActive = true}
            };
    }
 
    public ObservableCollection<Gender> Genders { get; set; }
    public ObservableCollection<Person> Persons { get; set; }
}

So, I'm convinced I'm setting properties wrong on the GridViewComboBoxColumn or setting the wrong properties. 
What is wrong with the above scenario?

[Maya]

Hello Brady,

Please take another look at our documentation. In this case you need to work with ItemsSource instead.  ItemsSourceBinding should be used when you have a collection property in the definition of the business object of the grid - in this case to have Genders property in Person class.

Regards,
Maya
Telerik