New Post: Cannot close SplitButton dropdown using IsOpen property.

<Window x:Class="WpfApplication93.MainWindow"
        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:local="clr-namespace:WpfApplication93"
        xmlns:xctk="http://schemas.xceed.com/wpf/xaml/toolkit"
        mc:Ignorable="d"
        Title="MainWindow">
    <Grid>
      <xctk:SplitButton x:Name="MyButton"
                        Width="300"
                        Height="50"
                        Content="AddThing">
         <xctk:SplitButton.DropDownContent>
            <ItemsControl HorizontalAlignment="Left">
               <ItemsControl.Resources>
                  <Style TargetType="MenuItem">
                     <Setter Property="StaysOpenOnClick"
                              Value="False" />
                  </Style>
               </ItemsControl.Resources>
               <MenuItem Click="OnClickOne"
                           Header="AddThing" />
               <MenuItem Click="OnClickTwo"
                           Header="AddOtherThing" />
            </ItemsControl>
         </xctk:SplitButton.DropDownContent>
      </xctk:SplitButton>
   </Grid>
</Window>

namespace WpfApplication93
{
  public partial class MainWindow : Window
  {
    public MainWindow()
    {
      InitializeComponent();
    }

    private void OnClickOne( object sender, RoutedEventArgs e )
    {
      MyButton.IsOpen = false;
    }

    private void OnClickTwo( object sender, RoutedEventArgs e )
    {
      MyButton.IsOpen = false;
    }
  }
}