EasyBindings

In English

UPD:

At the time of the development of this library, I was unaware of the existence of libraries such as Rx.NET and ReactiveUI, which allow you to do much more (and much better) than EasyBindings. Due to the existence of the mentioned libraries, this library becomes a public archive.

What is it?

EasyBindings is a tiny C# library that allows you perform trigger, property and command bindings, as in WPF.

What is it for?

EasyBindings makes it possible to use a WPF-specific mechanism for binding properties, triggers and commands outside of any MVVM framework.

What led to the creation of EasyBindings?

When I started developing a near-game project on the Godot engine and having experience in developing WPF projects, I really missed having a binding mechanism. I was looking for a library that would allow me to do similar things, but I didn't find it; so I decided to create one.

Additional

• The library code is documented and tested.
• EasyBindings uses the official Community Toolkit.Mvvm library from Microsoft, which provides tools for developing applications using the MVVM pattern.

Examples

Classes used in examples

• TextInput

using CommunityToolkit.Mvvm.ComponentModel;

public partial class TextInput : ObservableObject
{
    [ObservableProperty]
    private string _text = string.Empty;
}

• Button

using System;
using EasyBindings.Interfaces;

public class Button : ICommandExecutor
{
    public bool CanExecuteCommand { get; set; }

    public event Action? CommandExecutionRequested;

    public void Press()
    {
        if (CanExecuteCommand == false)
        {
            Console.WriteLine("Button can't be pressed.");
            return;
        }

        Console.WriteLine("Button was pressed.");
        CommandExecutionRequested?.Invoke();
    }
}

• Person

using CommunityToolkit.Mvvm.ComponentModel;

partial class Person : ObservableObject, IChangeable
{
    public object? State { get; }

    [NotifyPropertyChangedFor(nameof(State))]
    [ObservableProperty]
    private string _name = string.Empty;

    [NotifyPropertyChangedFor(nameof(State))]
    [ObservableProperty]
    private int _age;
}

• PersonObserver

using EasyBindings.Interfaces;

class PersonObserver : IUnsubscribe
{
    public void Observe(IChangeable changeable) =>
        TriggerBinder.OnPropertyChanged(this, changeable, o => o.State, () => Console.WriteLine($"{changeable}'s state was changed"));

    public void Unsubscribe() => TriggerBinder.Unbind(this);
}

Creating trigger bindings

• Bind trigger to property changed event:

// Create the observable object
var person = new Person();

// Create dummy text inputs to input text
var nameTextInput = new TextInput();
var ageTextInput = new TextInput();

// Bind person.Name to nameTextInput.Text
PropertyBinder.BindOneWay(this, person, t => t.Name, nameTextInput, s => s.Text);
// Bind person.Name to ageTextInput.Text using value converter
PropertyBinder.BindOneWay(this, person, t => t.Age, ageTextInput, s => s.Text,
    ageText => int.TryParse(ageText, out var age) ? age : 0);

// Enter text
nameTextInput.Text = "Ilnaz"; // person.Name also will be set to Ilnaz
ageTextInput.Text = "20"; // person.Age also will be set to 20

• Bind trigger to property changing event:

// Create the observable object with initial property value
var person = new Person
{
    Name = "Alfred"
};

// Create the trigger that will display person's name before it will be changed
TriggerBinder.OnPropertyChanging(this, person, o => o.Name, currentName =>
    Console.WriteLine($"Person's name will be changed; current name: {currentName}"));

// Change person's name
person.Name = "Ilnaz"; // Console output: Person's name will be changed; current name: Alfred

• Bind trigger to collection changed event:

// Create the observable collection
var numbers = new ObservableCollection<int>();
// Create the variable that stores sum of the numbers
var numbersSum = 0;

// Create the trigger that will update numberSum variable when numbers collection will change
TriggerBinder.OnCollectionChanged(this, numbers, () => numbersSum = numbers.Sum());

// Add some numbers to collection
numbers.Add(10); // numbersSum = 10
numbers.Add(20); // numbersSum = 30
numbers.Add(-30); // numbersSum = 0

Creating property binding

// Create the observable object
var person = new Person();

// Create dummy text inputs to input text
var nameTextInput = new TextInput();
var ageTextInput = new TextInput();

// Bind person.Name to nameTextInput.Text
PropertyBinder.BindOneWay(this, person, t => t.Name, nameTextInput, s => s.Text);
// Bind person.Name to ageTextInput.Text using value converter
PropertyBinder.BindOneWay(this, person, t => t.Age, ageTextInput, s => s.Text,
    ageText => int.TryParse(ageText, out var age) ? age : 0);

// Enter text
nameTextInput.Text = "Ilnaz"; // person.Name also will be set to Ilnaz
ageTextInput.Text = "20"; // person.Age also will be set to 20

Creating command binding

// Create the command to greet user with the given name
var greetCommand = new RelayCommand<string>
(
    execute: userName => Console.WriteLine($"Hello, {userName}!"),
    canExecute: userName => string.IsNullOrWhiteSpace(userName) == false
);

// Create the text input to enter name
var nameTextInput = new TextInput();
// Create the trigger that will notify command execution ability is changed
TriggerBinder.OnPropertyChanged(this, nameTextInput, o => o.Text, greetCommand.NotifyCanExecuteChanged);

// Create the button that will execute a command
var greetButton = new Button();

// Bind the command to the button
CommandBinder.Bind(this, greetButton, greetCommand, () => nameTextInput.Text);

// Change textInput's text
nameTextInput.Text = "Ilnaz";
greetButton.Press(); // Console output: Button was pressed.\nHello, Ilnaz!

nameTextInput.Text = string.Empty;
greetButton.Press(); // Console output: Button can't be pressed.

Using IChangeable interface

// Create the new person object
var person = new Person();

// Bind the trigger to person's state property changed event
TriggerBinder.OnPropertyChanged(this, person, o => o.State, () =>
    Console.WriteLine($"Person's state was changed: Name: {person.Name}, Age: {person.Age}."));

// Change person's properties
person.Name = "Ilnaz"; // Console output: Person's state was changed: Name: Ilnaz, Age: 0.
person.Age = 20; // Console output: Person's state was changed: Name: Ilnaz, Age: 20.

// Don't forget to unbind trigger
TriggerBinder.UnbindPropertyChanged(this, person);

Using IUnsubscribe interface

// Create two person objects
Person person1 = new(),
        person2 = new();

// Create the person observer object
var personObserver = new PersonObserver();
// Start observing persons
personObserver.Observe(person1);
personObserver.Observe(person2);

// Change persons properties
person1.Name = "Ilnaz"; // Console output: Person { Name = Ilnaz, Age = 0 }'s state was changed
person1.Age = 20; // Console output: Person { Name = Ilnaz, Age = 20 }'s state was changed

person2.Name = "Alfred"; // Console output: Person { Name = Alfred, Age = 0 }'s state was changed

// When you are not more need in object state changed notifier object,
// you should call unsubscribe method to clean up subscriptions
personObserver.Unsubscribe();

You can find more examples in EasyBindings.Tests project.