Implementation of Memento Pattern in VB.net

What is Memento Pattern?
Sometimes we want to perform undo with the changes. In such case situations memento helps.

Let’s look below code.

Imports System.Collections.Generic
Imports System.Linq
Imports System.Text
Imports System.Collections
Imports System.Diagnostics

Namespace TestMemento

	Class OriginalObject
		Public Property Name() As String
			Get
				Return m_Name
			End Get
			Set
				m_Name = Value
			End Set
		End Property
		Private m_Name As String
		Public Property SetMomento() As Momento
			Get
				Return m_SetMomento
			End Get
			Set
				m_SetMomento = Value
			End Set
		End Property
		Private m_SetMomento As Momento

		Public Sub New(Name As String)
			Me.Name = Name
			Me.SetMomento = New Momento(Name)
		End Sub

		Public Sub ChangeData()
			Me.Name = "Changed Name"
			Console.WriteLine(SetMomento.Name)
		End Sub

		Public Sub Revert()
			Console.WriteLine(SetMomento.Name)
		End Sub
	End Class

	Class Momento
		Public Property Name() As String
			Get
				Return m_Name
			End Get
			Set
				m_Name = Value
			End Set
		End Property
		Private m_Name As String
		Public Sub New(Name As String)
			Me.Name = Name
		End Sub
	End Class


	Class Program
		Private Shared Sub Main(args As String())
			Dim obj As New OriginalObject("This is original name")
			obj.ChangeData()
			obj.Revert()
			Console.ReadLine()
		End Sub
	End Class
End Namespace

In this case the Momento class plays the vital role.It stores the original value and when the ChangeData() is called then the new value is printed. Again when the Revert() is called, then it picks up the value from SetMomento.Name property and the original value retains.