Public Class Person
    Private m_name As String = "未設定"
    Public Property Name() As String
        Get
            Return m_name
        End Get
        Set(ByVal Value As String)
            m_name = Value
        End Set
    End Property
End Class

Public Class Child
    Inherits Person
    Private m_schoolName As String = "未設定"
    Public Property SchoolName() As String
        Get
            Return m_schoolName
        End Get
        Set(ByVal Value As String)
            m_schoolName = Value
        End Set
    End Property
End Class

Public Class Adult
    Inherits Person
    Private m_companyName As String = "未設定"
    Public Property CompanyName() As String
        Get
            Return m_companyName
        End Get
        Set(ByVal Value As String)
            m_companyName = Value
        End Set
    End Property
End Class

Public Class Persons
    <XmlArrayItem(Type:=GetType(Child)), _
    XmlArrayItem(Type:=GetType(Adult))> _
    Public persons(2) As Person

    Public Sub SetPersons(ByVal person1 As Person, ByVal person2 As Person, ByVal person3 As Person)
        persons(0) = person1
        persons(1) = person2
        persons(2) = person3
    End Sub

    Public Sub Dump()
        For Each person As Person In persons
            System.Diagnostics.Trace.WriteLine(person.Name)
            If TypeOf person Is Child Then
                System.Diagnostics.Trace.WriteLine(CType(person, Child).SchoolName)
            Else
                System.Diagnostics.Trace.WriteLine(CType(person, Adult).CompanyName)
            End If
        Next
    End Sub
End Class