Common mistakes

Common mistakes

Table 13.1 lists the mistakes that occur most often when working with data binding and MVVM.

Table 13.1. Common data binding and MVVM mistakes

Problem	Cause	Fix
a value does not appear or is not updated	an error in Path, a field instead of a property, no INotifyPropertyChanged	XAML Binding Failures, SetProperty, [ObservableProperty]
a new collection item does not appear in the list	List<T> instead of ObservableCollection<T>	ObservableCollection<T>
prices appear as $1,299.00 regardless of the user's regional settings	the elements' Language defaults to en-US	override the LanguageProperty metadata
a button with a command does not become enabled after the data changes	CanExecuteChanged was not raised	RaiseCanExecuteChanged, [NotifyCanExecuteChangedFor]
an implicit TextBlock style in App.xaml changes the button text	styles from application resources also apply inside templates	implicit TextBlock styles in the window resources