mvvm – Page 3 – Tarik Billa

Two Way Binding to AvalonEdit Document Text using MVVM

December 19, 2023 by Tarik

Create a Behavior class that will attach the TextChanged event and will hook up the dependency property that is bound to the ViewModel. AvalonTextBehavior.cs public sealed class AvalonEditBehaviour : Behavior<TextEditor> { public static readonly DependencyProperty GiveMeTheTextProperty = DependencyProperty.Register(“GiveMeTheText”, typeof(string), typeof(AvalonEditBehaviour), new FrameworkPropertyMetadata(default(string), FrameworkPropertyMetadataOptions.BindsTwoWayByDefault, PropertyChangedCallback)); public string GiveMeTheText { get { return (string)GetValue(GiveMeTheTextProperty); } set { … Read more

Concrete examples of state sharing between multiple viewmodels (WPF MVVM)

December 17, 2023 by Tarik

A typical way to achieve this is to use a messenger to publish a CarSelected message that details the selected car. Zero or more ViewModels can subscribe to the CarSelected message. ViewModels that are interested in the currently selected car can listen for the message and then act accordingly. The messenger approach provides a clean … Read more

MVVM and IOC: Handling View Model’s Class Invariants

December 17, 2023 by Tarik

I’m not quite sure what the issue is, so I’ll use a simple and contrived example. Let’s say you have a CustomerListViewModel which lists a summary of each customer. When you select a customer, you want to display a CustomerDetailViewModel. This could take either a customer ID, or an ICustomer type which is populated previously … Read more

MVVM and nested view models

December 17, 2023 by Tarik

You are on the right track. The parent model would naturally contain a list of child models, e.g. a customer having multiple orders. When ParentViewModel is created and loaded by a third-party, it is passed a ParentModel. Then the ParentViewModel will: Assign the ParentModel to a local variable Create a ChildViewModel for each ChildModel by … Read more

Duplicate class found in the file ‘/activity_login.xml’ DataBinding, BR not being generated

December 17, 2023 by Tarik

prism vs mvvm light for wpf

December 16, 2023 by Tarik

I just moved a project from Prism to MvvmLight and it seems to work faster (very subjective). Both Prism and MvvmLight have Mediator realisation (IEventAggregator in Prism, IMessenger in MvvmLight). But IMessenger has more abilities (for instance, sending messages with tokens) compared to IEventAggregator and is much more convenient to use (see next item). MvvmLight … Read more

WPF MVVM hiding button using BooleanToVisibilityConverter

December 13, 2023 by Tarik

For starters mate, if you’re using a Command, then you don’t need to bind IsEnabled, the command implementation should decide this. Secondly, the binding of a ViewModel to a View tends to happen at a bit of a later stage, so it’s best to also set a default value for the binding, like so Visibility=”{Binding … Read more

MVVM Light Messenger – Sending and Registering Objects

December 12, 2023 by Tarik

Jesse Liberty of Microsoft has a great concrete walk through on how to make use of the messaging within MVVM Light. The premise is to create a class which will act as your message type, subscribe, then publish. public class GoToPageMessage { public string PageName { get; set; } } This will essentially send the … Read more

MVVM where to put Data Access Layer?

December 10, 2023 by Tarik

Here’s how I’ve been organizing my MVVM w/ LINQ projects: Model – I think of the Model as the state of the system. It provides an interface to the data, and it keeps track of system status. The Model does not know about the ViewModel or View–it just provides a public interface to its data … Read more

Implementing CollectionChanged

December 10, 2023 by Tarik

You have to add a PropertyChanged listener to each item (which must implement INotifyPropertyChanged) to get notification about editing objects in a observable list. public ObservableCollection<Item> Names { get; set; } public List<Item> ModifiedItems { get; set; } public ViewModel() { this.ModifiedItems = new List<Item>(); this.Names = new ObservableCollection<Item>(); this.Names.CollectionChanged += this.OnCollectionChanged; } void OnCollectionChanged(object … Read more