RadComboBox + RadGridView = bug ?

[jimmy yang]

I put a RadComboBox in RadGridView and set the RadGridView's height a small value. Run the application, RadGridView will display the VerticalScrollBar automatically. I found that after scroll the VerticalScrollBar up or down serveral times, the RadComBox's items dispeared. Is it a bug?
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MainPage.xaml :

<UserControl x:Class="RadControlsBug.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"
mc:Ignorable="d" d:DesignWidth="640" d:DesignHeight="480">
<Grid x:Name="LayoutRoot">
<telerik:RadGridView ItemsSource="{Binding Employees,Mode=TwoWay}" ShowGroupPanel="False" RowIndicatorVisibility="Collapsed" CanUserFreezeColumns="False" Margin="10" AutoGenerateColumns="False" Height="90" Width="300" >
<telerik:RadGridView.Columns>

<telerik:GridViewColumn Header="Name">
<telerik:GridViewColumn.CellTemplate>
<DataTemplate>
<telerik:RadMaskedTextInput Width="100" Value="{Binding Name,Mode=TwoWay}" TextMode="PlainText" Margin="5"></telerik:RadMaskedTextInput>
</DataTemplate>
</telerik:GridViewColumn.CellTemplate>
</telerik:GridViewColumn>

<telerik:GridViewColumn Header="Sex">
<telerik:GridViewColumn.CellTemplate>
<DataTemplate>
<telerik:RadComboBox ItemsSource="{Binding SexList,Mode=TwoWay}" SelectedValue="{Binding Sex,Mode=TwoWay}" SelectedValuePath="Value" DisplayMemberPath="Text" Margin="5" >

</telerik:RadComboBox>
</DataTemplate>
</telerik:GridViewColumn.CellTemplate>
</telerik:GridViewColumn>
</telerik:RadGridView.Columns>
</telerik:RadGridView>
</Grid>
</UserControl>

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MainPage.xaml.cs:

using System.Windows;
using System.Windows.Controls;
using RadControlsBug.Model;

namespace RadControlsBug
{
public partial class MainPage : UserControl
{
private Company _viewModel = new Company();

public MainPage()
{
InitializeComponent();

this.Loaded += new RoutedEventHandler(MainPage_Loaded);
}

void MainPage_Loaded(object sender, RoutedEventArgs e)
{
_viewModel.Employees.Add(new Employee() { Name = "Jimmy", Sex = "M" });
_viewModel.Employees.Add(new Employee() { Name = "Mike", Sex = "M" });
_viewModel.Employees.Add(new Employee() { Name = "Jack", Sex = "M" });
_viewModel.Employees.Add(new Employee() { Name = "Rose", Sex = "F" });
_viewModel.Employees.Add(new Employee() { Name = "Kate", Sex = "F" });
this.DataContext = _viewModel;
}
}
}

-----------------------------------------------
Company.cs

using System.Collections.ObjectModel;

namespace RadControlsBug.Model
{
public class Company
{
public string CompanyName { set; get; }

private ObservableCollection<Employee> _employees = new ObservableCollection<Employee>();

public ObservableCollection<Employee> Employees
{
get { return _employees; }
set { _employees = value; }
}
}
}

--------------------------------------------------------
Employee.cs

using System.Collections.Generic;

namespace RadControlsBug.Model
{
public class Employee
{
public string Name { set; get; }

public string Sex { set; get; }

public List<TextValueObject> SexList {
get { return SexCollection.SexList; }
}
}
}

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TextValueObject.cs

namespace RadControlsBug.Model
{
public class TextValueObject
{
public string Text { set; get; }
public string Value { set; get; }
}
}

-------------------------------------------
SexCollection.cs

using System.Collections.Generic;

namespace RadControlsBug.Model
{
public static class SexCollection
{
private static List<TextValueObject> _SexList = new List<TextValueObject>();

public static List<TextValueObject> SexList
{
get { return SexCollection._SexList; }

}

static SexCollection()
{
_SexList.Add(new TextValueObject() { Text = "Male", Value = "M" });
_SexList.Add(new TextValueObject() { Text = "Female", Value = "F" });
}
}
}