![]() Public BindingsPage( BindingsViewModel viewModel)ĭone. xaml.cs file): public partial class BindingsPage : ContentPage Once this is done, we still need to set the BindingContext for the View in the code-behind (the View's. Here, I pass the name of the ViewModel including its namespace, so that it's fully qualified, because only fully-qualified names can be used in XAML compilation. DataType and BindingContextįirst, we need to set the x:DataType attribute of our ContentPage or ContentView on the root node in the XAML file to the underlying data type of the BindingContext of our View, which usually is a ViewModel: More recent versions of Xamarin.Forms also have XAML compilation enabled by default when using the official XAML templates. For Xamarin.Forms it needs to be explicitly enabled, either globally or locally. Note: For compiled bindings to be usable, you need make sure that XAML compilation is enabled in your project, which is the default for. Basically, all we need to do is setting the BindingContext property and the x:DataType attribute in the View and we're good to go (almost at least - there are some common pitfalls that I'll explain further down). The central component for compiled bindings is the x:DataType attribute, which exists in both Xamarin.Forms and. Private void RemoveItem( BindingItem item = null) Private ObservableCollection _items = new() Example ViewModelįor the bindings in this article, I will use the following, simplified ViewModel (you can find the full code in the sample repository ), which has a property called Items of type ObservableCollection, an AddItemCommand to add new items and a RemoveItemCommand to remove either the last item or a specific item, depending on the CommandParameter that is passed in of type BindingItem: public partial class BindingsViewModel : ObservableObject NET MAUI project (check out the sample repository ), but these concepts largely apply also to Xamarin.Forms. However, compiled bindings also exist in Windows Presentation Foundation (WPF), but they work quite differently and won't be covered in this blog article.įor this blog post, I will use a. You should definitely use them**, if you can**.**ĭisclaimer: This focus of this article is on compiled bindings in Xamarin.Forms and. According to Microsoft, compiled bindings are up to 20 times (!) faster than classic bindings**. In order to speed up data binding and provide compile-time evaluation of binding expressions (and also allow Intellisense and other tools to provide useful suggestions during design-time), compiled bindings were introduced. Lastly, classic bindings require some additional work in order to get useful code-completion suggestions and error messages in the XAML editor window.Įnter compiled bindings. Finding these types of bugs can turn out to be a time consuming and finicky task. This means that any incorrect bindings will only be noticed during runtime and potentially cause a crash or at the least a somewhat malfunctioning application. Secondly, because of this runtime resolution, binding expressions are not evaluated during compile-time. Worst of all, they are slow and inefficient, because classic bindings are resolved during runtime using reflection, which means that the binding source and target are scanned for matching properties and commands. NET based applications comes with a couple of drawbacks, though. This concept is used to access data from a data source (such as properties inside a ViewModel) from within the user interface and react to changes that may occur during runtime. NET MAUI before, you are likely familiar with a common concept called data binding. ![]() NET-based UI frameworks like Xamarin.Forms and.
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