UWP Development, Understanding Code Behind Merged with View and ViewModel

Understanding Code Behind Merged Views and ViewModels in UWP Development

UWP (Universal Windows Platform) development is a powerful platform for building applications that can run on a variety of Microsoft devices. The MVVM (Model-View-ViewModel) architecture is widely used in UWP application development, and understanding the interaction between UWP’s view and view model is crucial.

1. Understanding the MVVM Architecture

MVVM is a design pattern implemented in UWP applications that clearly defines the structure of the application and separates the code to facilitate maintenance and testing. MVVM is primarily composed of the following three components:

  • Model: Contains the application’s data and business logic.
  • View: Represents the user interface (UI) and interacts with the user.
  • ViewModel: Acts as an intermediary between the view and model, preparing the data needed for the view and handling user actions.

This design pattern increases code reuse and enables more efficient application development through the separation of UI and business logic.

2. Combining View and ViewModel in UWP

In UWP, views are defined using XAML, while C# is used on the backend to implement the view models. The view and view model are connected via data binding. Through data binding, the view can observe the properties of the view model in real-time, and events that occur in the view (e.g., button clicks) are passed to the view model to perform appropriate logic.

2.1. Features of Data Binding

The data binding in UWP has the following characteristics:

  1. Data Context: Assign a view model instance using the DataContext property of the view.
  2. Property Change Notification: By implementing the INotifyPropertyChanged interface, notifications can be sent to the UI when properties change.
  3. Commands: Use the ICommand interface to pass events occurring in the view as commands to the view model.

2.2. Example Code

Let’s examine the combination of views and view models in a UWP application through the following example.

 
// Model
public class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
}

// ViewModel
using System.ComponentModel;

public class PersonViewModel : INotifyPropertyChanged
{
    private Person person;
    
    public PersonViewModel()
    {
        Person = new Person { Name = "John Doe", Age = 30 };
    }

    public Person Person
    {
        get => person;
        set
        {
            person = value;
            OnPropertyChanged(nameof(Person));
        }
    }

    public string DisplayName => $"{Person.Name}, {Person.Age} years old";

    public event PropertyChangedEventHandler PropertyChanged;

    protected virtual void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

3. Data Transfer from ViewModel to View

Now let’s look at how to bind data from the view model to update it in the view. We will add a simple logic to change the property of the view model on button click.

 
// MainPage.xaml.cs
private PersonViewModel viewModel;

public MainPage()
{
    this.InitializeComponent();
    viewModel = new PersonViewModel();
    this.DataContext = viewModel;
}

private void OnChangeNameClicked(object sender, RoutedEventArgs e)
{
    viewModel.Person.Name = "Jane Doe"; // Change name
    viewModel.OnPropertyChanged(nameof(viewModel.DisplayName)); // Update DisplayName
}

4. Conclusion

Now we have understood the integration and data flow between views and view models in UWP. The MVVM architecture increases the maintainability of the code and allows for a clear separation of UI and application logic. In this article, we explained the interaction between views and view models through a basic example. Building on this foundation, more complex applications can be developed.

More information about UWP development will be provided in the future, so please stay tuned!