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Xamarin Community Toolkit DelegateWeakEventManager

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An event Delegate implementation that enables the garbage collector to collect an object without needing to unsubscribe event handlers.

Inspired by Xamarin.Forms.WeakEventManager, expanding the functionality of Xamarin.Forms.WeakEventManager to support Delegate events.

Syntax

public DelegateWeakEventManager()

Methods

Methods Return Type Description
AddEventHandler(Delegate, string eventName) void Adds the event handler.
RemoveEventHandler(Delegate, string eventName) void Removes the event handler.
HandleEvent(object, object, string void Invokes the event EventHandler.
HandleEvent(string void Invokes the event Action.
RaiseEvent(object, object, string void Invokes the event EventHandler.
RaiseEvent(string void Invokes the event Action.

Examples

This section shows how to use this type.

Use Delegate

readonly DelegateWeakEventManager _propertyChangedEventManager = new DelegateWeakEventManager();

public event PropertyChangedEventHandler? PropertyChanged
{
    add => _propertyChangedEventManager.AddEventHandler(value);
    remove => _propertyChangedEventManager.RemoveEventHandler(value);
}

void OnPropertyChanged([CallerMemberName]string propertyName = "") => _propertyChangedEventManager.RaiseEvent(this, new PropertyChangedEventArgs(propertyName), nameof(PropertyChanged));

Use EventHandler

readonly DelegateWeakEventManager _canExecuteChangedEventManager = new DelegateWeakEventManager();

public event EventHandler CanExecuteChanged
{
    add => _canExecuteChangedEventManager.AddEventHandler(value);
    remove => _canExecuteChangedEventManager.RemoveEventHandler(value);
}

void OnCanExecuteChanged() => _canExecuteChangedEventManager.RaiseEvent(this, EventArgs.Empty, nameof(CanExecuteChanged));

Use Action

readonly DelegateWeakEventManager _weakActionEventManager = new DelegateWeakEventManager();

public event Action ActionEvent
{
    add => _weakActionEventManager.AddEventHandler(value);
    remove => _weakActionEventManager.RemoveEventHandler(value);
}

void OnActionEvent(string message) => _weakActionEventManager.RaiseEvent(message, nameof(ActionEvent));

API