Introduction to Avalonia

Avalonia is a modern, cross-platform UI framework built on .NET. Inspired by WPF but designed to run on multiple operating systems including Windows, Linux, and macOS, Avalonia offers a powerful solution for desktop application development.

Key Features

• True Cross-Platform Support: Consistent experience across different operating systems
• High Performance: Leverages .NET Core's performence capabilities
• XAML-based UI: Declarative markup language for building interfaces
• Rich Data Binding: Powerful binding system for connecting UI and data
• MVVM Support: Built-in support for Model-View-ViewModel pattern

Getting Started

Installation

1. Install .NET SDK from official website
2. Choose an IDE (Visual Studio or JetBrains Rider recommended)
3. Install Avalonia templates:

dotnet new --install Avalonia.Templates

Creating Your First Project

dotnet new avalonia.app -n MyAvaloniaApp
cd MyAvaloniaApp
dotnet run

Core Concepts

XAML Basics

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Welcome">
    <StackPanel>
        <TextBlock Text="Hello, Avalonia!" 
                   HorizontalAlignment="Center"/>
        <Button Content="Click Me!" 
                HorizontalAlignment="Center"
                Margin="0,20,0,0"/>
    </StackPanel>
</Window>

Data Binding

<TextBlock Text="{Binding UserName}"/>

Styling

<Style Selector="Button">
    <Setter Property="Background" Value="#3498db"/>
    <Setter Property="Foreground" Value="White"/>
</Style>

MVVM Implementation

ViewModel Example

public class MainViewModel : ReactiveObject
{
    private string _searchTerm;
    public string SearchTerm
    {
        get => _searchTerm;
        set => this.RaiseAndSetIfChanged(ref _searchTerm, value);
    }

    public ReactiveCommand<Unit, Unit> SearchCommand { get; }

    public MainViewModel()
    {
        SearchCommand = ReactiveCommand.Create(PerformSearch);
    }

    private void PerformSearch()
    {
        // Search logic here
    }
}

Advanced Features

Custom Controls

public class RatingControl : Control
{
    public static readonly StyledProperty<int> ValueProperty = 
        AvaloniaProperty.Register<RatingControl, int>(nameof(Value));

    public int Value
    {
        get => GetValue(ValueProperty);
        set => SetValue(ValueProperty, value);
    }
}

Animation

<Button Content="Animated Button">
    <Button.Transitions>
        <Transitions>
            <TransformOperationsTransition Property="RenderTransform" 
                                         Duration="0:0:0.2"/>
        </Transitions>
    </Button.Transitions>
</Button>

Performance Optimization

Virtualization

<ListBox Items="{Binding LargeData}"
         VirtualizationMode="Simple">
    <!-- Item template -->
</ListBox>

Compiled Bindings

<TextBlock Text="{CompiledBinding UserName}"/>

Testing

Unit Test Example

[Fact]
public void AddItemCommand_Should_Add_New_Item()
{
    var vm = new MainViewModel();
    vm.NewItemName = "Test";
    vm.AddItemCommand.Execute(null);
    
    Assert.Single(vm.Items);
    Assert.Equal("Test", vm.Items[0].Name);
}

Deployement

Platform-Specific Builds

# Windows
dotnet publish -c Release -r win-x64 --self-contained true

# macOS
dotnet publish -c Release -r osx-x64 --self-contained true

# Linux
dotnet publish -c Release -r linux-x64 --self-contained true