Wires is a simple binding library for frameworks that doesn't have built-in mecanisms. Many choices have been made to have a restrictive base API. A wide set of extensions are also packaged for Xamarin.iOS and Xamarin.Android.

Several other solutions exist, but I've experienced a lot of memory issues with these : that's why I've decided to initiate my own binding library.

Available on NuGet

To bind data to components with extensions, simply use those fluent APIs :

this.ViewModel
		    .Bind(this.label)
		    	.Text(vm => vm.Title, Converters.Uppercase)
			.Bind(this.field)
		    	.Text(vm => vm.Title)
			.Bind(this.image)
		    	.ImageAsync(vm => vm.Illustration)
		    	.Alpha(vm => vm.Amount)
		    	.Visible(vm => vm.IsActive)
			.Bind(this.toggleSwitch)
		    	.On(vm => vm.IsActive)
			.Bind(this.slider)
		    	.Value(vm => vm.Amount)
			.Bind(this.datePicker)
		    	.Date(vm => vm.Birthday)
			.Bind(this.progressView)
		    	.Progress(vm => vm.Amount)
			.Bind(this.activityIndicator)
		    	.IsAnimating(vm => vm.IsLoading)
			.Bind(this.segmented)
		    	.Titles(vm => vm.Sections)
			.Bind(this.button)
		    	.TouchUpInside(vm => vm.LoadCommand);

Value converters can also be used with an IConverter<TSource,TTarget> implementation, or a lambda expression :

this.ViewModel
		.Bind(this.label)
			.TextColor(vm => vm.IsValid, new RelayConverter<bool,UIColor>(x => x ? UIColor.Green : UIColor.Red));

• UIView
  • Visible bool
  • Hidden bool
  • TintColor UIColor
  • BackgroundColor UIColor
  • Alpha nfloat
• UIActivityIndicator
  • IsAnimating bool
• UIButton
  • TouchUpInside ICommand
  • Title string
  • Image UIImage
• UIDatePicker
  • Date DateTime
• UIProgressView
  • Progress double
  • ProgressTintColor UIColor
  • TrackTintColor UIColor
• UIImageView
  • Image UIImage
  • ImageAsync UIImage
• UILabel
  • Text string
  • TextColor UIColor
• UISegmentedControl
  • Titles string[]
  • Selected int
• UISlider
  • Value float
  • MaxValue float
  • MinValue float
• UIStepper
  • Value double
  • MaximumValue double
  • MinimumValue double
• UISwitch
  • On bool
• UITextField
  • Text string
• UIViewController
  • Title string
  • BackTitle string
• UIWebView / WKWebView
  • HtmlContent string

Wires provides more basic APIs on which are based all the extensions.

this.ViewModel.Bind(custom).Property(vm => vm.Source, x => x.Target);
this.ViewModel.Bind(custom).Property<TSourceType, TTargetType, EventArgs>(vm => vm.Source, x => x.Value, nameof(Custom.ValueChanged));

You also observe a property with ObserveProperty : the given action will be invoked and again each time the property changes.

this.ViewModel.Bind(this.label).ObserveProperty(vm => vm.Title, (vm,label,title) => { label.Text = title; });

For more advanced options see Binder<TSource,TTarget> APIs, or simply take a look at provided extensions to create your own ones.

If no converter is given, an default one will be chosen from the registered ones (with Converters.Register<TSource,TTarget>(converter)).

• Shared
  • <float, double> : casting value
  • <double, float> : casting value
  • <long, DateTime> : from a millisecond timestamp to a datetime.
• iOS
  • <int,nint> : casting value
  • <uint,nuint> : casting value
  • <float,nfloat> : casting value
  • <double,nfloat> : casting value
  • <int,nfloat> : casting value
  • <DateTime,NSDate> : from managed type to native one
  • <int,UIColor> : an hexadecimal raw value from 0xAARRGGBB to a native color
  • <string,UIColor> : an hexadecimal text value from "#AARRGGBB" to a native color
  • <string,UIImage> : from a bundle image name to an image instance

Specific converter can be used when binding, a several common converters are available.

• Shared
  • Converters.Identity<T>() : creates a IConverter<T,T> that returns the given value in both ways.
  • Converters.Invert : a IConverter<bool,bool> that inverts the given boolean value.
  • Converters.Uppercase : a IConverter<string,string> that change the given string to uppercase.
  • Converters.Lowercase : a IConverter<string,string> that change the given string to lowercase.
  • new RelayConverter<TSource,TTarget>(...) : an easy way to implement a converter from lambdas.
• iOS
  • PlatformConverters.AsyncStringToCachedImage(TimeSpan expiration) : at first request ,downloads image from http location and stores it into local storage. The next times (until the expiration date is reached), the cached image will be returned.

Wires provides also helpers for binding collection sources to UITableView(iOS), UICollectionView(iOS) and ListView(Android).

this.ViewModel.Bind(this.tableView).Source<RedditViewModel, RedditViewModel.ItemViewModel, PostTableCell>(vm => vm.Simple, (post, index, cell) => cell.ViewModel = post, heightForItem: (c) => 88);
this.ViewModel.Bind(this.tableView).Source<RedditViewModel,string, RedditViewModel.ItemViewModel,PostTableHeader, PostTableCell>(vm => vm.Grouped, (section, index, cell) => cell.ViewModel = section, (post, index, cell) => cell.ViewModel = post, selectItemCommand, (headerIndex) => 68, (cellIndex) => 88);

this.ViewModel.Bind(this.collectionView).Source<RedditViewModel, RedditViewModel.ItemViewModel, PostCollectionCell>(vm => vm.Simple, (post, index, cell) => cell.ViewModel = post);
this.ViewModel.Bind(this.collectionView).Source<RedditViewModel, string, RedditViewModel.ItemViewModel, PostCollectionHeader, PostCollectionCell>(vm => vm.Grouped, (section, index, cell) => cell.ViewModel = section, (post, index, cell) => cell.ViewModel = post, selectItemCommand);

Take a look at samples to see it in action.

In most cases, you don't have to worry about unbinding because Wires purges all bindings regulary if sources of targets have been garbage collected.

But if you reuse a view, and want to update bindings you have to remove the previous bindings before. It is a common with recycling collection patterns (UITableViews, UICollectionViews, Adapters).

This is available through Unbind(this TSsource, params object[] targets) extension.

this.viewmodel.Unbind(label, this.image, this.title)

You can also use Rebind method to unbind just before binding.

this.ViewModel.Rebind(this.label).Text(v => v.Title)

If you want to observe an event without keeping a strong reference to your subscriber, use a WeakEventHandler instead. You don't have to worry about unscription anymore in most cases!

public override void ViewDidLoad()
{
	base.ViewDidLoad();
	this.ViewModel = new RedditViewModel();
	this.ViewModel.AddWeakHandler<PropertyChangedEventArgs>(nameof(INotifyPropertyChanged.PropertyChanged), this.OnViewModelPropertyChanged);
}

private void OnViewModelPropertyChanged(object sender, PropertyChangedEventArgs args)
{
	if(args == nameof(this.ViewModel.Title)
	{
	  // ...
	}
}

• Improve architecture
• Improve tests
• Android extensions
• Bindable adapters on Android
• Cleaner code
• More documentation
• Trottling functiunalities
• Command parameters

Contributions are welcome! If you find a bug please report it and if you want a feature please report it.

If you want to contribute code please file an issue and create a branch off of the current dev branch and file a pull request.

MIT © Aloïs Deniel