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reactiveui / ReactiveUI


An advanced, composable, functional reactive model-view-viewmodel framework for all .NET platforms that is inspired by functional reactive programming. ReactiveUI allows you to abstract mutable state away from your user interfaces, express the idea around a feature in one readable place and improve the testability of your application.



Use the Reactive Extensions for .NET to create elegant, testable User Interfaces that run on any mobile or desktop platform.

Supported Platforms

  • Xamarin.iOS
  • Xamarin.Android
  • Xamarin.Mac
  • WPF
  • Windows Forms
  • Windows Phone 8
  • Windows Store Apps

This library is organized into several high-level assemblies:

  • ReactiveUI - Core library that doesn't rely on any particular UI framework. ReactiveObject, the base ViewModel object, as well as ReactiveCollection, a more awesome ObservableCollection, is in here.

  • ReactiveUI.Xaml - Classes that require references to a Xaml'ly framework, like WPF or WinRT. ReactiveCommand, an implementation of ICommand, as well as the UserError classes are in this assembly.

  • ReactiveUI.Blend - This class has several Blend Behaviors and Triggers that make attaching ViewModel changes to Visual State Manager states.

  • ReactiveUI.Routing - A screens and navigation framework as well as ViewModel locator. This framework helps you to write applications using IoC containers to locate views, as well as navigating back and forwards between views.

A Compelling Example

public class ColorChooserThatDoesntLikeGreen : ReactiveObject
  // Declaring a read/write property

  byte _Red;
  public byte Red {
    get { return _Red; }
    set { this.RaiseAndSetIfChanged(value); }

  byte _Green;
  public byte Green {
    get { return _Green; }
    set { this.RaiseAndSetIfChanged(value); }

  byte _Blue;
  public byte Blue {
    get { return _Blue; }
    set { this.RaiseAndSetIfChanged(value); }

  // Declaring a Property that's based on an Observable

  ObservableAsPropertyHelper<Color> _Color;
  public Color Color {
    get { return _Color.Value; }

  ReactiveCommand OkButton { get; protected set; }

  public ColorChooserThatDoesntLikeGreen()
    var finalColor = this.WhenAny(x => x.Red, x => x.Green, x => x.Blue, 
        (r,g,b) => Color.FromRGB(r.Value, g.Value, b.Value));

    finalColor.ToProperty(this, x => x.Color, out _Color);

    // When the finalColor has full green, the Ok button is disabled
    OkButton = new ReactiveCommand(finalColor.Select(x => x.Green != 255));

Learn more

For more information on how to use ReactiveUI, check out ReactiveUI.