Reactive Library Overview

The SciChart.UI.Reactive library provides observable viewmodels which combine INotifyPropertyChanged event notifications for WPF, and Reactive IObservable streams for observing individual, or combinations of properties.

NuGet Package

Dependencies for SciChart.UI.Reactive

• Log4Net 2.0.8
• System.Reactive 4.1.0
• Unity 5.8.11

Key Types Included in SciChart.UI.Reactive

ViewModelBase

A ViewModel type which implements INotifyPropertyChanged only, no reactive, and no Finalizer. Supports dynamic properties for get/set (more on this below).

e.g.

// Lightweight viewmodel which does not implement the Finalizer pattern, 
// does not support Rx and is suitable for rapid instantiation e.g. ListBoxItem ViewModels or search results
public class MyLightweightViewModel : ViewModelBase
{
	// A boolean property 
	public bool AProperty
	{
		// Backing fields mimicked by dictionary. 
		get => GetDynamicValue<bool>();
		// Setting sets the value and raises INotifyPropertyChanged for property "AProperty"
		set => SetDynamicValue(value);
	}
}

ObservableObjectBase

A ViewModel type which implements INotifyPropertyChanged, IDisposable, IObservableObject the Finalizer Pattern and supports PropertyChanged notifications via Rx (Reactive Extensions)

e.g.

// Viewmodel which which implements INotifyPropertyChanged, IObservableOject, IDisposable
// Supports Rx and can subscribe to property changed notifications on any property 
public class MyReactiveViewModel : ObservableObjectBase
{
	public MyReactiveViewModel()
	{
		// WhenPropertyChanged returns IObservable<bool> for property AProperty
		this.WhenPropertyChanged(x => x.AProperty)
			// Subscribe to the observable
			.Subscribe(newValue => Console.WriteLine($"NewValue is {newValue}!"))
			// Ensure disposable of subscription with parent
			.DisposeWith(this);
	}

	// A boolean property 
	public bool AProperty
	{
		// Backing fields mimicked by dictionary. 
		get => GetDynamicValue<bool>();
		// Setting sets the value and raises INotifyPropertyChanged for property "AProperty"
		// Also pushes a new value through the ObservableObjectBase.PropertyChangedSubject 
		set => SetDynamicValue(value);
	}
}

ViewModelWithTraitsBase

This type builds upon ObservableObject by providing traits - a neat way to store complex behaviours related to one or more operations in the ViewModel in one place.

Dependencies to the Traits are automatically injected if they are registered in a UnityContainer provided by ViewContext.Container.

public class Program
{
	static void Main()
	{
		// For traits to work they expect ViewContext.Container to be a UnityContainer instance
		var container = new UnityContainer();
		ViewContext.Container = container;

		// and dependent types to be registered. 
		// See SciChart.UI.Bootstrap for how to auto-register using the 
		// [ExportType] attribute 
		container.RegisterType<ISomeDependency, SomeDependency>();
	}
}


public interface ISomeDependency
{
	void WriteLine(string line);
}

// Here's my dependency, which gets auto-injected into the constructor of MyTrait 
public class SomeDependency : ISomeDependency
{
	public void WriteLine(string line)
	{
		Console.WriteLine(line);
	}
}

// The trait is a class for putting groups of behaviours with dependencies specified by Unity in one place
// It is attached to the ViewModel using the WithTrait<T> function 
public class MyTrait : ViewModelTrait<MyReactiveViewModelWithTraits>
{
	public MyTrait(MyReactiveViewModelWithTraits target, ISomeDependency someDependency) : base(target)
	{
		// WhenPropertyChanged returns IObservable<bool> for property AProperty
		Target.WhenPropertyChanged(x => x.AProperty)
			// Subscribe to the observable
			.Subscribe(newValue => someDependency.WriteLine($"NewValue is {newValue}!"))
			// Ensure disposable of subscription with parent
			.DisposeWith(this);
	}
}

// Viewmodel which which implements INotifyPropertyChanged, IObservableOject, IDisposable
// Supports Rx and can subscribe to property changed notifications on any property 
public class MyReactiveViewModelWithTraits : ViewModelWithTraitsBase
{
	public MyReactiveViewModelWithTraits()
	{
		this.WithTrait<MyTrait>();           
	}

	// A boolean property 
	public bool AProperty
	{
		// Backing fields mimicked by dictionary. 
		get => GetDynamicValue<bool>();
		// Setting sets the value and raises INotifyPropertyChanged for property "AProperty"
		// Also pushes a new value through the ObservableObjectBase.PropertyChangedSubject 
		set => SetDynamicValue(value);
	}
}