Introduction

The SQuan.Helpers.Maui.Mvvm package is designed to supplement the CommunityToolkit.Mvvm package with .NET MAUI-specific source-generators to simplify creating observable properties or bindable properties on .NET MAUI bindable objects.

Getting started

To install the package from within Visual Studio:

1. In Solution Explorer, right-click on the project and select "Manage NuGet Packages". Search for "SQuan.Helpers.Maui.Mvvm" and install it.
2. Add a using or Imports directive to use the new APIs:

using SQuan.Helpers.Maui.Mvvm;

3. Set the language version in your project file to access preview features:

<PropertyGroup>
   <LangVersion>preview</LangVersion>
</PropertyGroup>

Examples

CardView Example

You can use [BindableProperty] to reduce the code needed to extend ContentView to create a custom control. The following example shows the CardTitle bindable property in the code-behind file to the CardView class:

public partial class CardView : ContentView
{
    [BindableProperty] public partial string CardTitle { get; set; } = string.Empty;
    // ...

    public CardView()
    {
        InitializeComponent();
    }
}

Count Example

You can use [ObservableProperty] to reduce the code needed to add properties to a ContentPage. The following example turns Count into an observable property in the code-behind file of the MainPage class:

public partial class MainPage : ContentPage
{
    [ObservableProperty] public partial int Count { get; set; } = 0;

    public MainPage()
    {
        InitializeComponent();
        CounterBtn.SetBinding(
            Button.TextProperty,
            static (MainPage ctx) => ctx.Count,
            BindingMode.OneWay,
            source: this,
            stringFormat: "Clicked {0} times");
    }

    void OnCounterClicked(object sender, EventArgs e)
    {
        Count++;
        SemanticScreenReader.Announce(CounterBtn.Text);
    }
}

Attributes

BindableProperty

Adds bindable properties to a bindable object.

[BindableProperty] public partial string CardTitle { get; set; } = string.Empty;

ObservableProperty

Adds observable properties to a bindable object with OnPropertyChanged() notifications.

[ObservableProperty] public partial int Count { get; set; } = 0;

NotifyPropertyChangedFor

Makes additional calls to a bindable object's OnPropertyChanged() method.

public partial class MainPage
{
    [ObservableProperty, NotifyPropertyChangedFor("FullName")] public partial string FirstName { get; set; } = string.Empty;
    [ObservableProperty, NotifyPropertyChangedFor("FullName")] public partial string LastName { get; set; } = string.Empty;
    public string FullName => $"{FirstName} {LastName}";
}

NotifyPropertyChangingFor

Makes additional calls to a bindable object's OnPropertyChanging() method.

Events

For generated observable properties and bindable properties, additional partial methods may be implemented.

partial void On{PropertyName}Changing({PropertyType} value);
partial void On{PropertyName}Changing({PropertyType} oldValue, {PropertyType} newValue);
partial void On{PropertyName}Changed({PropertyType} value);
partial void On{PropertyName}Changed({PropertyType} oldValue, {PropertyType} newValue);

For example:

public partial class MainPage
{
    [ObservableProperty] public int Count { get; internal set; } = 0;

    public void OnCountChanged(int oldValue, int newValue)
    {
        Trace.WriteLine($"Count changed from {oldValue} to {newValue}");
    }
}