Public Overridable Property fDisconnection() As Nullable(Of Boolean)

        Get
            Return Me._fDisconnection
        End Get
        Set(value As Nullable(Of Boolean))
            If ((Me._fDisconnection = value) _
               = False) Then  ‘此处赋值将无法执行，默认_fDisconnection 为nothing, 判断永远为跳出,
                Me.sendPropertyChanging()
                Me._fDisconnection = value    ‘_fDisconnection 永远无法获得值
                Me.sendPropertyChanged(“fDisconnection”)
            End If
        End Set
    End Property