ghuntley / WeakEventListener

The WeakEventListener allows the owner to be garbage collected if its only remaining link is an event handler.

WeakEventListener

The WeakEventListener allows the owner to be garbage collected if its only remaining link is an event handler. See https://docs.microsoft.com/en-us/dotnet/framework/wpf/advanced/weak-event-patterns for more information; the wisdom found on that page is applicable for other platforms inc UWP, Xamarin.Mac, Xamarin.iOS & Xamarin.Android.

Supported Platforms

• netstandard v1.1 (and up)

Installation

Installation is done via NuGet:

PM> Install-Package WeakEventListener

Usage

public class SampleClass
{
    public event EventHandler<EventArgs> Raisevent;

    public void DoSomething()
    {
        OnRaiseEvent();
    }

    protected virtual void OnRaiseEvent()
    {
        Raisevent?.Invoke(this, EventArgs.Empty);
    }
}

public void Test_WeakEventListener_Events()
{
    bool isOnEventTriggered = false;
    bool isOnDetachTriggered = false;

    SampleClass sample = new SampleClass();

    WeakEventListener<SampleClass, object, EventArgs> weak = new WeakEventListener<SampleClass, object, EventArgs>(sample);
    weak.OnEventAction = (instance, source, eventArgs) => { isOnEventTriggered = true; };
    weak.OnDetachAction = (listener) => { isOnDetachTriggered = true; };

    sample.Raisevent += weak.OnEvent;

    sample.DoSomething();
    Assert.True(isOnEventTriggered);

    weak.Detach();
    Assert.True(isOnDetachTriggered);
}

With thanks to

• The WeakEventListener was promoted from the UWPCommunityToolkit to become this package.