一个“>”导致我调试了1个小时才解决问题

在XAML里面写了如下的代码：

<DataTemplate x:Key="DT_HintCategory">
<Expander HorizontalContentAlignment="Stretch"
ExpandDirection="Down"
Expanded="Expander_Expanded"
Header="AAA"
IsExpanded="{Binding Path=IsExpanded,
Mode=TwoWay}">
<Expander.Content>
<ListBox x:Name="PART_HINTS" IsSynchronizedWithCurrentItem="False">>
<ListBox.ItemsSource>
<PriorityBinding>
<Binding Path="HintsSlow" IsAsync="True" />
<Binding Path="HintsFast" IsAsync="False" />
</PriorityBinding>
</ListBox.ItemsSource>
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding Name}" />
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Expander.Content>
</Expander>
</DataTemplate>

原因就是： <ListBox x:Name="PART_HINTS" IsSynchronizedWithCurrentItem="False">>（多写了一个大于号！）

结果在设计界面显示：An Unhandled Exception has occured: Click here to reload the designer.

在调试过程中，报：

{"Add value to collection of type 'System.Windows.Controls.ItemCollection' threw an exception."}

Inner Exception:　{"Operation is not valid while ItemsSource is in use. Access and modify elements with ItemsControl.ItemsSource instead."}