DateTimePicker: fixed dropdown when IsReadOnly = true

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/DateTimePicker/Themes/Generic.xaml

@@ -103,7 +103,8 @@
                                 <ToggleButton x:Name="_calendarToggleButton" Grid.Column="1" Background="White"
                                               IsChecked="{Binding IsOpen, RelativeSource={RelativeSource TemplatedParent}}"
                                               Style="{StaticResource DateTimePickerToggleButtonStyle}"
-                                              IsHitTestVisible="{Binding IsOpen, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource InverseBoolConverter}}"/>
+                                              IsHitTestVisible="{Binding IsOpen, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource InverseBoolConverter}}"
+                                              IsEnabled="{Binding IsReadOnly, RelativeSource={RelativeSource TemplatedParent}, Converter={StaticResource InverseBoolConverter}}" />
                             </Grid>
                             <Popup IsOpen="{Binding IsChecked, ElementName=_calendarToggleButton}" StaysOpen="False">
                                 <Border BorderThickness="1" Background="{StaticResource PopupBackgroundBrush}" BorderBrush="{StaticResource PopupDarkBorderBrush}" Padding="3">