Both C# and VB.NET can declare custom events that determine what happens when someone subscribes or unsubscribes from an event, and how the subscribers list is stored. Note that the VB.NET example is more verbose, but it enables you to control how the event is actually raised. In this case, each handler is called asynchronously for concurrent access. The RaiseEvent waits for all events to be fully raised before resuming:
C#
List<EventHandler> EventHandlerList = new List<EventHandler>(); public event EventHandler Click{ add{EventHandlerList.Add(value);} remove{EventHandlerList.Remove(value);} }
VB.NET
Private EventHandlerList As New ArrayList Public Custom Event Click As EventHandler AddHandler(ByVal value As EventHandler) EventHandlerList.Add(value) End AddHandler RemoveHandler(ByVal value As EventHandler) EventHandlerList.Remove(value) End RemoveHandler RaiseEvent(ByVal sender As Object, ByVal e As EventArgs) Dim results As New List(Of IAsyncResult) For Each handler As EventHandler In EventHandlerList If handler IsNot Nothing Then results.Add(handler.BeginInvoke(sender, e, Nothing, Nothing)) End If Next While results.Find(AddressOf IsFinished) IsNot Nothing Threading.Thread.Sleep(250) End While End RaiseEvent End Event Private Function IsFinished(ByVal async As IAsyncResult) As Boolean Return async.IsCompleted End Function
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