VB.NET 中的委託與事件一例

Namespace Events
    Public Delegate Sub NumberReachedEventHandler(ByVal sender As Object, ByVal e As NumberReachedEventArgs)

    Public Class Counter
        Public Event NumberReached As NumberReachedEventHandler

        Public Sub New()
        End Sub

        Public Sub CountTo(ByVal countTo As Integer, ByVal reachableNum As Integer)
            If countTo < reachableNum Then Throw New ArgumentException("reachableNum should be less than countTo")

            For ctr As Integer = 0 To countTo

                If ctr = reachableNum Then
                    Dim e As NumberReachedEventArgs = New NumberReachedEventArgs(reachableNum)
                    OnNumberReached(e)
                    Return
                End If
            Next
        End Sub

        Protected Overridable Sub OnNumberReached(ByVal e As NumberReachedEventArgs)
            RaiseEvent NumberReached(Me, e)
        End Sub
    End Class

    Public Class NumberReachedEventArgs
        Inherits EventArgs

        Private _reached As Integer

        Public Sub New(ByVal num As Integer)
            Me._reached = num
        End Sub

        Public ReadOnly Property ReachedNumber As Integer
            Get
                Return _reached
            End Get
        End Property
    End Class

End Namespace

此代碼取自CODEPROJECT.COM，放在這裏，僅供學習使用