WeakEventManager.ListenerList Class
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WeakEventManager.ListenerList Class


Provides a built-in collection list for storing listeners for a WeakEventManager.

Namespace:   System.Windows
Assembly:  WindowsBase (in WindowsBase.dll)


protected class ListenerList


Initializes a new instance of the WeakEventManager.ListenerList class.


Initializes a new instance of the WeakEventManager.ListenerList class with the specified initial capacity.


Gets the number of items contained in the WeakEventManager.ListenerList.


Gets a value that represents an empty list for purposes of comparisons.


Gets a value that declares whether this WeakEventManager.ListenerList is empty.


Gets or sets a specific listener item in the WeakEventManager.ListenerList .


Adds a IWeakEventListener object to the WeakEventManager.ListenerList.


Adds an event handler to the WeakEventManager.ListenerList.


Declares the list to be in use. This prevents direct changes to the list during iterations of the list items.


Creates a modifiable clone of this WeakEventManager.ListenerList.


Copies the current WeakEventManager.ListenerList to the specified WeakEventManager.ListenerList

System_CAPS_pubmethodDeliverEvent(Object, EventArgs, Type)

Delivers the event being managed to each listener in the WeakEventManager.ListenerList.


Unlocks the locked state initiated by BeginUse.


Determines whether the specified object is equal to the current object.(Inherited from Object.)


Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)


Serves as the default hash function. (Inherited from Object.)


Gets the Type of the current instance.(Inherited from Object.)


Creates a shallow copy of the current Object.(Inherited from Object.)


Checks to see whether the provided list is in use, and if so, sets the list reference parameter to a copy of that list rather than the original.


Removes all entries from the list where the underlying reference target is a null reference.


Removes the first occurrence of a listener item from the WeakEventManager.ListenerList.


Removes an event handler from the WeakEventManager.ListenerList.


Returns a string that represents the current object.(Inherited from Object.)

Although this list contains members that resemble those defined by IList and ICollection, and provide similar functionality, this class implements neither of those interfaces.

Most WeakEventManager derived classes do not need to use any members on WeakEventManager.ListenerList. The WeakEventManager methods ProtectedAddListener and ProtectedRemoveListeneruse a default WeakEventManager.ListenerList internally, one list for each source.

You only need to call WeakEventManager.ListenerList methods if your WeakEventManager class maintains multiple lists for the same event-source combination, with each list created to account for different conditions of the event. In this case, you would not use ProtectedAddListener and ProtectedRemoveListener and would instead implement AddListener or RemoveListener to act upon listeners in just one of the internal listener lists, typically based on a parameter that you add to AddListener or RemoveListener. Also, the handler implementation that receives the raw event cannot simply call DeliverEvent; you must instead keep track of the specifics of the event and deliver the event only to the appropriate list using DeliverEventToList.

The various methods of WeakEventManager.ListenerList are provided so that you can work with your internal lists and so that you can prevent modification of the list during actual delivery of the event.

An example class that used this implementation technique is PropertyChangedEventManager, which maintains separate listener lists for PropertyChanged based on which property changed.

You cannot use this class in XAML.

.NET Framework
Available since 3.0

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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