HamburgerMenuItem IsEnabled property cannot be updated on runtime - wpf

Question

I am having a problem updating the IsEnabled property from HamburgerMenuItem.
First, I set the value of IsEnabledProperty to be false, and then during runtime, I am trying to change it to true, but debugger keeps saying that the value is false. And, of course the UI also still shows that it is disabled. Below is the code:
View:
xmlns:controls="http://metro.mahapps.com/winfx/xaml/controls"
<UserControl.Resources>
<DataTemplate x:Key="MenuItemTemplate" DataType="{x:Type metro:HamburgerMenuGlyphItem}">
<Grid Height="50">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="50"/>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<TextBlock Grid.Column=0 Text="{Binding Glyph}"/>
<TextBlock Grid.Column=1 Text="{Binding Label}"/>
</Grid>
</DataTemplate>
</UserControl.Resources>
<controls:x:Name="HamburgerMenuControl"
DisplayMode="CompactInline"
ItemTemplate="{StaticResource MenuItemTemplate}"
ItemsSource="{Binding MenuItems, Mode=OneWay}"/>
<Button Content="Test Button" Command="{Binding TestCommand, Mode=OneTime}"/>
ViewModel:
private HamburgerMenuItemCollection menuItems;
public HamburgerMenuItemCollection MenuItems
{
get {return menuItems;}
set {SetProperty(ref menuItems, value);}
}
public ICommand TestCommand {get; private set;}
public MyVM()
{
MenuItems = new HamburgerMenuItemCollection()
{
new HamburgerMenuGlyphItem()
{
Glyph="1",
Label="1"
};
// Second MenuItem is disabled
new HamburgerMenuGlyphItem()
{
Glyph="2",
Label="2",
IsEnabled=false;
};
};
TestCommand = new DelegateCommand(UpdateIsEnabled);
}
private void UpdateIsEnabled()
{
var menuItem = MenuItems[1];
menuItem.IsEnabled = true; // after this is executed, Debugger shows that IsEnabled is still false;
if (menuItem.IsEnabled != isEnabled)
{
vm.BeginInvoke(() =>
{
vm.IsEnabled = isEnabled; // redo, but it seems like none of these are called
vm.SetValue(HamburgerMenuGlyphItem.IsEnabledProperty, isEnabled);
vm.SetCurrentValue(HamburgerMenuGlyphItem.IsEnabledProperty, isEnabled);
vm.InvalidateProperty(HamburgerMenuGlyphItem.IsEnabledProperty);
}, System.Windows.Threading.DispatcherPriority.Normal);
}
RaisePropertyChanged(nameof(MenuItems));
}
Can you show me what I did wrong and how to update the IsEnabled Dependency Property properly?

Answer 1

To enable the HamburgerMenuItem you should sets its Command property to a command whose CanExecute method returns true.
You cannot just set the IsEnabled property to true. If you take a look at how the HamburgerMenuItem class is implemented on GitHub, you'll see that there is a CoerceValueCallback that returns the value of the private CanExecute method:
private static object IsEnabledCoerceValueCallback(DependencyObject d, object value)
{
if (!(bool)value)
{
return false;
}
return ((HamburgerMenuItem)d).CanExecute;
}