GoodbyeXAML.Avalonia 0.0.1

Installing

Add one of the following nuget packages to your project:

• GoodbyeXAML.Wpf.Framework for the WPF .Net Framework version
• GoodbyeXAML.Wpf.Core for the WPF .Net Core version
• GoodbyeXAML.Avalonia for the Avalonia version

What is GoodbyeXAML?

GoodbyeXAML is a collection of extension methods that lets helps you lay out WPF or Avalonia UIs using declarative C#, rather than XAML.

For example, here's a simple "Hello world" window in XAML:

    <Window x:Class="MyApp.MainWindow"
                xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
                xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
                xmlns:local="clr-namespace:MyApp"
                mc:Ignorable="d">
        <TextBlock Text="Hello world" />
    </Window>

With GoodbyeXAML, we can create the same window in pure C#:

    using System.Windows;
    using System.Windows.Controls;
    using GoodbyeXAML.Wpf.Shared;

    namespace MyApp
    {
        public class MainWindow : Window
        {
            public MainWindow()
            {
                this.Content = new TextBlock()
                    ._Text("Hello world!");
            }
        }
    }

_Text is an extension method that sets TextBlock's Text property. Every property on every Control has a corresponding extension method that sets its value and returns the Control you called it on. That means you can chain multiple calls like this:

new TextBlock()
    ._Text("Hello world!")
    ._Background(Brushes.Black)
    ._Foreground(Brushes.White);

Using this technique, you can create trees of Controls just like you can in XAML:

new StackPanel()
    ._Orientation(Orientation.Vertical)
    ._HorizontalAlignment(HorizontalAlignment.Center)
    ._VerticalAlignment(VerticalAlignment.Center)
    ._Children
    (
        new TextBlock()._Text("Hello"),
        new TextBlock()._Text("World"),
        new StackPanel()
            .Orientation(Orientation.Horizontal)
            ._Children
            (
                new TextBlock()._Text("I'm "),
                new TextBlock()._Text("a "),
                new TextBlock()._Text("nested "),
                new TextBlock()._Text("StackPanel!")
            )
    );

Unlike with XAML, though, you have access to all of the language constructs built into C#. For example, we can extract new TextBlock()._Text("Blah") into a separate function, since we keep repeating it so much:

public static TextBlock Label(string text)
{
    return new TextBlock()
        ._Text(text);
}

Or preferrably, we can use C#'s alternate syntax:

public static TextBlock Label(string text) => new TextBlock()
    ._Text(text);

Now our earlier code can be refactored to look like:

new StackPanel()
    ._Orientation(Orientation.Vertical)
    ._HorizontalAlignment(HorizontalAlignment.Center)
    ._VerticalAlignment(VerticalAlignment.Center)
    ._Children
    (
        Label("Hello"),
        Label("World"),
        new StackPanel()
            .Orientation(Orientation.Horizontal)
            ._Children
            (
                Label("I'm "),
                Label("a "),
                Label("nested "),
                Label("StackPanel!")
            )
    );

If we later want to change all of those TextBlocks (for example, to give them a dark theme), we only need to change the Label function. It is, after all, just a function!

public static TextBlock Label(string text) => new TextBlock()
    ._Text(text)
    ._Background(Brushes.Black)
    ._Foreground(Brushes.White);

Or maybe we don't want them to be TextBlocks after all-- maybe we want them to be buttons! Why? Because I said so, that's why!

public static TextBlock Label(string text) => new Button()
    ._Content(text)
    ._Click((s, e) => MessageBox.Show(text))

Properties aren't the only things that have these extenion methods-- all public facing events do too! And because we're using C#, we can use a lambda expression as our event handler. That way we don't need to write all of the usual boilerplate just for a one-line event handler.

Of course, you can still use a delegate instead of a lambda expression, just like you would in XAML:

public static TextBlock Label(string text) => new Button()
    ._Content(text)
    ._Click(Label_Click)

private static void Label_Click(object sender, RoutedEventArgs args)
{
    var btn = (Button)sender;
    var text = (string)(btn.Content);

    MessageBox.Show(text);
}

I hope now you can see just how flexible this technique is---far moreso than XAML!

Lambda binding

TODO: Explain what lambda binding is, and how cool it is.

Building

Before you can build any of the projects in the GoodbyeXAML folder, you first need to run CodeGenerator. Open CodeGenerator/CodeGenerator.sln in Visual Studio and click "run". This will generate a bunch of shared projects and dump them into the folder GeneratedExtensionMethods.

Now you can open GoodbyeXAML/GoodbyeXAML.sln in Visual Studio and build the individual projects at your leisure.

At some point, I will write a script or something to automated this.