DelegateBindings

Easy property bindings using delegates, with the help of Nito.Mvvm.CalculatedProperties.

How to use it

First you need view models implemented like this:

public class RootViewModel : INotifyPropertyChanged
{
	private readonly PropertyHelper properties;

	public RootViewModel()
	{
		properties = new(RaisePropertyChanged);
	}

	public event PropertyChangedEventHandler? PropertyChanged;

	private void RaisePropertyChanged(PropertyChangedEventArgs args) =>
		PropertyChanged?.Invoke(this, args);

	public string Text
	{
		get => properties.Get("");
		set => properties.Set(value);
	}

	public ObservableCollection<Item> Items =>
		properties.Get(() => new ObservableCollection<Item>());
}

public class ItemViewModel : INotifyPropertyChanged
{
	private readonly PropertyHelper properties;

	public ItemViewModel()
	{
		properties = new(RaisePropertyChanged);
	}

	public event PropertyChangedEventHandler? PropertyChanged;

	private void RaisePropertyChanged(PropertyChangedEventArgs args) =>
		PropertyChanged?.Invoke(this, args);

	public string Content
	{
		get => properties.Get("");
		set => properties.Set(value);
	}
}

Bind()

Then, it's just as simple as calling the binding like this:

using static DelegateBindings.DelegateBinder;

// ...

var binding1 = Bind(() => label1.Text = viewModel.Text);
var binding2 = Bind(() => label2.Text = viewModel.Items.FirstOrDefault()?.Content);

Whenever viewModel.Text changes, label1.Text will be changed as well.

It also works for observable collections. Whenever the Items list is updated, or the first item's Content is updated, label2.Text will also change.

WhenChanged()

Another alternative is to use WhenChanged() to subscribe to property changes.

using static DelegateBindings.DelegateBinder;

// ...

var binding3 = WhenChanged(() => viewModel.Text, x => Show(x));
var binding4 =
	WhenChanged(() => viewModel.Items.Count)
	.Subscribe(x => LogCount(x)); // Support for Rx.NET

void Show(string text)
{
	MessageBox.Show(text);
}

void LogCount(int count)
{
	Console.WriteLine($"We have {count} elements so far.");
}

Remarks

The Bind() method receives an Action, not an Expression, which means you're not limited by the C# features available in expressions.
The view models MUST be implemented with Nito.Mvvm.CalculatedProperties. If you're using other libraries, the bindings WON'T WORK.
Bindings are one-way. I'm planning to add two-way binding in the future but for now you can do two bindings like this: Bind(() => viewModel2.Result = viewModel1.Text); Bind(() => viewModel1.Text = viewModel2.Result); Or, for UI controls (WinForms, WPF, etc), use events directy: Bind(() => textBox.Text = viewModel1.Text); textBox.Validated += (_, _) => viewModel1.Text = textBox.Text;

License

MIT

R2D221/DelegateBindingsv1.1.0

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