Polymorphism/Serialization XmlSerializer (VB.NET)

Imports System.IO
Imports System.Collections
Imports System.Runtime.Serialization.Formatters.Binary
Imports System.Xml.Serialization

Module Module1

    Sub Main()
        'Create some objects
        Dim dObj() = New DrawingObject(3) {}

        dObj(0) = New Line(100, 100)
        dObj(1) = New Circle(50, 10, 10)
        dObj(2) = New Square(10, 10, 20, 20)
        dObj(3) = New DrawingObject()

        Serialize(dObj)

        Dim deserializedList = New List(Of DrawingObject)()
        ' deserialize to a generic list
        deserializedList = Deserialize(Of List(Of DrawingObject))()

        ' display the results
        For Each DrawingObject As DrawingObject In deserializedList

            Select Case DrawingObject.GetType().Name
                Case "Line"
                    Console.WriteLine(String.Format("I'm a {0}", DrawingObject.Draw()))
                    Dim line As Line = DirectCast(DrawingObject, Line)
                Case "Circle"
                    Console.WriteLine(String.Format("I'm a {0}", DrawingObject.Draw()))
                    Dim circle As Circle = DirectCast(DrawingObject, Circle)
                Case "Square"
                    Dim square As Square = DirectCast(DrawingObject, Square)
                    Console.WriteLine(String.Format("I'm a {0}", DrawingObject.Draw()))
                Case Else
                    Console.WriteLine(String.Format("I'm just a {0}", DrawingObject.Draw()))
            End Select
        Next

        Console.ReadLine()
    End Sub

    Private Sub Serialize(Of T)(data As T)

        ' Use a file stream here.
        Using WriteFileStream As New StreamWriter("test.xml")
            ' Construct a SoapFormatter and use it
            ' to serialize the data to the stream.
            Dim SerializerObj As New XmlSerializer(GetType(DrawingObject()))

            Try
                ' Serialize EmployeeList to the file stream
                SerializerObj.Serialize(WriteFileStream, data)
            Catch ex As Exception
                Console.WriteLine(String.Format("Failed to serialize. Reason: {0}", ex.Message))
            End Try
        End Using
    End Sub

    Private Function Deserialize(Of T)() As T
        Dim ReturnListOfT = CreateInstance(Of T)()

        ' Create a new file stream for reading the XML file
        Using ReadFileStream = New FileStream("test.xml", FileMode.Open, FileAccess.Read, FileShare.Read)
            ' Construct a XmlSerializer and use it
            ' to serialize the data from the stream.
            Dim SerializerObj = New XmlSerializer(GetType(T))

            Try
                ' Deserialize the hashtable from the file
                ReturnListOfT = DirectCast(SerializerObj.Deserialize(ReadFileStream), T)
            Catch ex As Exception
                Console.WriteLine(String.Format("Failed to serialize. Reason: {0}", ex.Message))
            End Try
        End Using
        ' return the Deserialized data.
        Return ReturnListOfT
    End Function

    ' function to create instance of T
    Private Function CreateInstance(Of T)() As T
        Return DirectCast(Activator.CreateInstance(GetType(T)), T)
    End Function

End Module

' The objects we are going to Serializing/De-serializing
<XmlInclude(GetType(Line))>
<XmlInclude(GetType(Circle))>
<XmlInclude(GetType(Square))>
<Serializable()>
Public Class DrawingObject

    Public Sub New()

    End Sub

    Public Overridable Function Draw() As String
        Return "generic drawing object."
    End Function
End Class

<Serializable()>
Public Class Square
    Inherits DrawingObject

    Public Overrides Function Draw() As String
        Return "Circle."
    End Function

    Public Sub New()
    End Sub

    Public Sub New(x1 As Integer, y1 As Integer, x2 As Integer, y2 As Integer)
        Me.X1 = x1
        Me.Y1 = y1
        Me.X2 = x2
        Me.Y2 = y2
    End Sub

    Public Property X1 As Integer
    Public Property Y1 As Integer

    Public Property X2 As Integer
    Public Property Y2 As Integer
End Class

<Serializable()>
Public Class Line
    Inherits DrawingObject

    Public Overrides Function Draw() As String
        Return "Line."
    End Function

    Public Sub New()
    End Sub

    Public Sub New(x As Integer, y As Integer)

        Me.X = x
        Me.Y = y
    End Sub

    Public Property X As Integer
    Public Property Y As Integer
End Class

<Serializable()>
Public Class Circle
    Inherits DrawingObject

    Public Overrides Function Draw() As String
        Return "Circle."
    End Function

    Public Sub New()
    End Sub

    Public Sub New(radius As Integer, x As Integer, y As Integer)
        Me.Radius = radius
        Me.X = x
        Me.Y = y
    End Sub

    Public Property Radius As Integer
    Public Property X As Integer
    Public Property Y As Integer

End Class