OutWit.Common.MVVM.Avalonia 2.0.4

OutWit.Common.MVVM.Avalonia

Avalonia-specific MVVM components and utilities, including source generator for automatic StyledProperty, DirectProperty, and AttachedProperty generation.

Features

• Source Generator for Properties: Automatically generate StyledProperty, DirectProperty, and AttachedProperty from attributes
• AvaloniaDispatcher: IDispatcher implementation for UI thread invocation
• Binding Utilities: Helper methods for property registration
• Visual Tree Traversal: Extension methods for navigating Avalonia visual tree
• BindingProxy: Binding proxy for DataContext access
• DataTemplate Utilities: Helper methods for DataTemplate creation

Installation

dotnet add package OutWit.Common.MVVM.Avalonia

This automatically includes:

• OutWit.Common.MVVM (base cross-platform package)
• OutWit.Common.MVVM.Avalonia.Generator (source generator)
• OutWit.Common.Logging

Quick Start

Source Generator for StyledProperty

The simplest way to create StyledProperties:

using Avalonia.Controls;
using OutWit.Common.MVVM.Avalonia.Attributes;

namespace MyApp.Controls
{
    public partial class CustomButton : Button
    {
        [StyledProperty(DefaultValue = "Click Me")]
        public string Label { get; set; }

        [StyledProperty(BindsTwoWayByDefault = true)]
        public bool IsPressed { get; set; }
    }
}

Important: Mark your class as partial to allow source generator to add code.

The generator automatically creates:

// Generated code (you don't write this):
public static readonly StyledProperty<string> LabelProperty = 
    AvaloniaProperty.Register<CustomButton, string>(nameof(Label), "Click Me");
public static readonly StyledProperty<bool> IsPressedProperty = 
    AvaloniaProperty.Register<CustomButton, bool>(nameof(IsPressed), defaultBindingMode: BindingMode.TwoWay);

DirectProperty for Performance

Use DirectProperty for frequently changing values (better performance, no style system participation):

public partial class CounterControl : Control
{
    [DirectProperty(DefaultValue = 0)]
    public int Counter { get; set; }

    [DirectProperty(BindsTwoWayByDefault = true)]
    public string Text { get; set; }
}

Generated code:

// Backing field is generated automatically
private int m_counter = 0;
public static readonly DirectProperty<CounterControl, int> CounterProperty = 
    AvaloniaProperty.RegisterDirect<CounterControl, int>(
        nameof(Counter), 
        o => o.m_counter, 
        (o, v) => o.m_counter = v,
        unsetValue: 0);

Attached Properties

using OutWit.Common.MVVM.Avalonia.Attributes;

public static partial class MyAttachedProperties
{
    [AttachedProperty(DefaultValue = false)]
    public static bool IsHighlighted { get; set; }

    [AttachedProperty(DefaultValue = 1.0, Inherits = true)]
    public static double Opacity { get; set; }
}

// Usage in AXAML:
// <Button local:MyAttachedProperties.IsHighlighted="True" />

Generated code includes Get/Set methods:

public static bool GetIsHighlighted(AvaloniaObject obj) => obj.GetValue(IsHighlightedProperty);
public static void SetIsHighlighted(AvaloniaObject obj, bool value) => obj.SetValue(IsHighlightedProperty, value);

Convention-Based Callbacks

The generator automatically discovers callback methods by naming convention:

public partial class SmartControl : Control
{
    // No need to specify OnChanged - automatically discovered!
    [StyledProperty(DefaultValue = "Hello")]
    public string Title { get; set; }

    // Convention: On{PropertyName}Changed
    private void OnTitleChanged(AvaloniaPropertyChangedEventArgs<string> e)
    {
        // Handle title change
    }

    // Convention: {PropertyName}Coerce
    private string TitleCoerce(AvaloniaObject sender, string value)
    {
        return value?.Trim() ?? "";
    }
}

Visual Tree Traversal

using OutWit.Common.MVVM.Avalonia.Utils;

// Find first child of specific type
var button = myPanel.FindFirstChildOf<Button>();

// Find all children
var allButtons = myPanel.FindAllChildrenOf<Button>();

// Find parent
var window = myButton.FindFirstParentOf<Window>();

BindingProxy for DataContext Access

<UserControl.Resources>
    <local:BindingProxy x:Key="Proxy" Data="{Binding}" />
</UserControl.Resources>

<DataGrid Items="{Binding Items}">
    <DataGrid.Columns>
        <DataGridTemplateColumn>
            <DataTemplate>
                <Button Command="{Binding Data.DeleteCommand, Source={StaticResource Proxy}}"
                        CommandParameter="{Binding}" />
            </DataTemplate>
        </DataGridTemplateColumn>
    </DataGrid.Columns>
</DataGrid>

AvaloniaDispatcher

using OutWit.Common.MVVM.Avalonia.Abstractions;

// Get dispatcher for current thread
var dispatcher = AvaloniaDispatcher.UIThread;

// Invoke on UI thread
dispatcher.Invoke(() => UpdateUI());

// Async invoke
await dispatcher.InvokeAsync(() => UpdateUI());

Property Types Comparison

StyledProperty Options

DirectProperty Options

AttachedProperty Options

Related Packages

• OutWit.Common.MVVM - Cross-platform base classes
• OutWit.Common.MVVM.WPF - WPF-specific implementation
• OutWit.Common.MVVM.Blazor - Blazor-specific implementation

License

Licensed under the Apache License, Version 2.0. See LICENSE.

Attribution (optional)

If you use OutWit.Common.MVVM.Avalonia in a product, a mention is appreciated (but not required), for example: "Powered by OutWit.Common.MVVM.Avalonia (https://ratner.io/)".

Trademark / Project name

"OutWit" and the OutWit logo are used to identify the official project by Dmitry Ratner.

You may:

• refer to the project name in a factual way (e.g., "built with OutWit.Common.MVVM.Avalonia");
• use the name to indicate compatibility (e.g., "OutWit.Common.MVVM.Avalonia-compatible").

You may not:

• use "OutWit.Common.MVVM.Avalonia" as the name of a fork or a derived product in a way that implies it is the official project;
• use the OutWit.Common.MVVM.Avalonia logo to promote forks or derived products without permission.