What are events?

As compared to the delegates events works with source and listener methodology. So the listeners who are interested in receiving few events they subscribe to the source. Once this subscription is completed the source raises events to its entire listener when required. One source can have many listeners. In the sample given below class "ClsWithEvents" is an event source class, which has a event "EventAddString()". Now the listeners who are interested in receiving these events they can subscribe to this event. In the class "FrmWithEvents" you can see they handle clause which is associated with the "mobjClsWithEvents" objects.

Public  Class ClsWithEvents

Event EventAddString(ByVal Value As String) Public Sub AddString()

RaiseEvent EventAddString("String added by Event") End Sub

End Class

Public Class FrmWithEvents

Inherits System.Windows.Forms.Form

Private WithEvents mobjClsWithEvents As New ClsWithEvents() Private Sub FrmWithEvents_Load(ByVal sender As System.Object,

ByVal e As System.EventArgs) Handles MyBase.Load

End Sub

Private Sub mobjClsWithEvents_EventAddString(ByVal Value As

String) Handles mobjClsWithEvents.EventAddString

LstData.Items.Add(Value) End Sub

Private Sub CmdRunEvents_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles CmdRunEvents.Click

mobjClsWithEvents.AddString() End Sub

End Class

Figure:-Events in action