public class ValueEventArgs : Inherits EventArgs
Private oldTemp As Decimal
Private newTemp As Decimal
Public ReadOnly Property OldValue As Decimal
Get
Return Me.oldTemp
End Get
End Property
Public ReadOnly Property NewValue As Decimal
Get
Return Me.newTemp
End Get
End Property
Public Sub New(oldTemp As Decimal, newTemp As Decimal)
Me.oldTemp = oldTemp
Me.newTemp = newTemp
End Sub
End Class
Public Delegate Sub ValueEventHandler(sender As Object,ev As ValueEventArgs)
Public Class ValueMonitor
Private currentValue As Decimal
Private threshholdValue As Decimal
Public Event ValueThreshold As ValueEventHandler
Public Sub New(threshHold As Decimal)
Me.threshholdValue = threshHold
End Sub
Public Sub SetValue(newValue As Decimal)
If (Me.currentValue > threshholdValue And _
newValue <= Me.threshholdValue) Or _
(Me.CurrentValue < Me.threshholdValue And _
newValue >= Me.threshholdValue) Then
OnRaiseValueEvent(newValue)
End If
Me.currentValue = newValue
End Sub
Public Function GetValue() As Decimal
Return Me.currentValue
End Function
Protected Overridable Sub OnRaiseValueEvent(newValue As Decimal)
RaiseEvent ValueThreshold(Me, New ValueEventArgs(Me.currentValue, _
newValue))
End Sub
End Class
Public Module Example
Public Sub Main()
Dim tempMon As New ValueMonitor(32d)
tempMon.SetValue(31)
Console.WriteLine("Current temperature is {0} degrees Fahrenheit.",tempMon.GetValue())
AddHandler tempMon.ValueThreshold, AddressOf TempMonitor
tempMon.SetValue(33)
Console.WriteLine("Current temperature is {0} degrees Fahrenheit.",tempMon.GetValue())
RemoveHandler tempMon.ValueThreshold, AddressOf TempMonitor
tempMon.SetValue(31)
Console.WriteLine("Current temperature is {0} degrees Fahrenheit.",tempMon.GetValue())
End Sub
Private Sub TempMonitor(sender As Object, e As ValueEventArgs)
Console.WriteLine("Value is changing from {0} to {1}.",e.OldValue, e.NewValue)
End Sub
End Module
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