ContextMenu is empty on first left-click of wpf button - wpf

Question

I have a button in my view with a dynamic context menu that I want to activate via right or left clicks. When I left-click first, the menu is empty. When I right-click, or left-click after a right-click, the menu shows with the contents of favouriteItemList.
I have looked at this, which looks like it might be an answer, but I don't understand enough about WPF to get it to work with my code.
The other thing is that SelectFavouriteCommand doesn't seem to be called when I click an item in the menu.
View model class:
{
public ViewModel(IFolderService folderService)
{
this.SelectFavouriteCommand = new MvxAsyncCommand(this.SelectFavourite);
this.favouriteItemList = new MvxObservableCollection<SelectedFolder>(folderService.GetFolders());
}
public IMvxAsyncCommand SelectFavouriteCommand { get; }
private MvxObservableCollection<SelectedFolder> favouriteItemList;
public MvxObservableCollection<SelectedFolder> FavouriteItemList
{
get => this.favouriteItemList;
set
{
this.favouriteItemList = value;
RaisePropertyChanged(() => this.FavouriteItemList);
}
}
private async Task SelectFavourite()
{
throw new NotImplementedException();
}
}
In the view xml:
<Button DockPanel.Dock="Right" x:Name="BtnUseFavourite" Height="25" Width="25" Margin="0,0,5,0">
<StackPanel>
<Image Source="/Images/ImageFavoriteIcon.png" />
</StackPanel>
<Button.Style>
<Style TargetType="{x:Type Button}">
<Style.Triggers>
<EventTrigger RoutedEvent="Click">
<EventTrigger.Actions>
<BeginStoryboard>
<Storyboard>
<BooleanAnimationUsingKeyFrames Storyboard.TargetProperty="ContextMenu.IsOpen">
<DiscreteBooleanKeyFrame KeyTime="0:0:0" Value="True"/>
</BooleanAnimationUsingKeyFrames>
</Storyboard>
</BeginStoryboard>
</EventTrigger.Actions>
</EventTrigger>
</Style.Triggers>
</Style>
</Button.Style>
<Button.ContextMenu>
<ContextMenu ItemsSource="{Binding FavouriteItemList}">
<ContextMenu.ItemContainerStyle>
<Style TargetType="MenuItem">
<Setter Property="Header" Value="{Binding Path=Path}"></Setter>
<Setter Property="Command" Value="{Binding SelectFavouriteCommand}" ></Setter>
</Style>
</ContextMenu.ItemContainerStyle>
</ContextMenu>
</Button.ContextMenu>
</Button>

Answer 1

For calling command try below code
<Setter Property="Command"
Value="{Binding Path=DataContext.SelectFavouriteCommand, RelativeSource={RelativeSource AncestorType={x:Type Window}}}"/>

Answer 2

For you to be able to invoke the SelectFavouriteCommand when clicking on the MenuItem, you should bind to the Button's DataContext using the PlacementTarget property of the ContextMenu:
<ContextMenu ItemsSource="{Binding FavouriteItemList}">
<ContextMenu.ItemContainerStyle>
<Style TargetType="MenuItem">
<Setter Property="Header" Value="{Binding Path=Path}"></Setter>
<Setter Property="Command" Value="{Binding PlacementTarget.DataContext.SelectFavouriteCommand,
RelativeSource={RelativeSource AncestorType=ContextMenu}}" />
</Style>
</ContextMenu.ItemContainerStyle>
</ContextMenu>
And a context menu is only expected to be opened when right-clicking on a Button. Left-clicking would invoke a command or a click event handler.