Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim io As New InputOutput(Val(TextBox1.Text))

        Dim num = New ParseDecimalToRoman()
        num.Interpret(io)

        TextBox2.Text = io.Output
    End Sub
End Class

Public MustInherit Class Terminals

    Inherits RomanExpression

    Public Overrides Sub Interpret(ByVal value As InputOutput)

        While value.Input - 9 * Multiply() >= 0

            value.Output += NineStrings()

            value.Input -= 9 * Multiply()

        End While

        While value.Input - 5 * Multiply() >= 0

            value.Output += FiveStrings()

            value.Input -= 5 * Multiply()

        End While

        While value.Input - 4 * Multiply() >= 0

            value.Output += FourStrings()

            value.Input -= 4 * Multiply()

        End While

        While value.Input - Multiply() >= 0

            value.Output += OneStrings()

            value.Input -= Multiply()

        End While

    End Sub

    Public MustOverride Function OneStrings() As String
    Public MustOverride Function FourStrings() As String
    Public MustOverride Function FiveStrings() As String
    Public MustOverride Function NineStrings() As String
    Public MustOverride Function Multiply() As Integer
End Class

Public Class InputOutput

    Private intIn As Integer
    Private strOut As String

    Public Sub New(ByVal intInput As Integer)

        Me.intIn = intInput

    End Sub

    Public Property Input() As Integer

        Get

            Return intIn

        End Get

        Set(ByVal value As Integer)

            intIn = value

        End Set

    End Property

    Public Property Output() As String

        Get

            Return strOut

        End Get

        Set(ByVal value As String)

            strOut = value

        End Set

    End Property

End Class

Public MustInherit Class RomanExpression

    Public MustOverride Sub Interpret(ByVal value As InputOutput)

End Class

Class Ones

    Inherits Terminals

    Public Overrides Function OneStrings() As String

        Return "I"

    End Function

    Public Overrides Function FourStrings() As String

        Return "IV"

    End Function

    Public Overrides Function FiveStrings() As String

        Return "V"

    End Function

    Public Overrides Function NineStrings() As String

        Return "IX"

    End Function

    Public Overrides Function Multiply() As Integer

        Return 1

    End Function

End Class

Class Tens

    Inherits Terminals

    Public Overrides Function OneStrings() As String

        Return "X"

    End Function

    Public Overrides Function FourStrings() As String

        Return "XL"

    End Function

    Public Overrides Function FiveStrings() As String

        Return "L"

    End Function

    Public Overrides Function NineStrings() As String

        Return "XC"

    End Function

    Public Overrides Function Multiply() As Integer

        Return 10

    End Function

End Class

Class Hundreds

    Inherits Terminals

    Public Overrides Function OneStrings() As String

        Return "C"

    End Function

    Public Overrides Function FourStrings() As String

        Return "CD"

    End Function

    Public Overrides Function FiveStrings() As String

        Return "D"

    End Function

    Public Overrides Function NineStrings() As String

        Return "CM"

    End Function

    Public Overrides Function Multiply() As Integer

        Return 100

    End Function

End Class

Class Thousands

    Inherits Terminals

    Public Overrides Function OneStrings() As String

        Return "M"

    End Function

    Public Overrides Function FourStrings() As String

        Return "MV"

    End Function

    Public Overrides Function FiveStrings() As String

        Return "V"

    End Function

    Public Overrides Function NineStrings() As String

        Return "MX"

    End Function

    Public Overrides Function Multiply() As Integer

        Return 1000

    End Function

End Class

Class TenThousands

    Inherits Terminals

    Public Overrides Function OneStrings() As String

        Return "X|"

    End Function

    Public Overrides Function FourStrings() As String

        Return "XL|"

    End Function

    Public Overrides Function FiveStrings() As String

        Return "L|"

    End Function

    Public Overrides Function NineStrings() As String

        Return "XC|"

    End Function

    Public Overrides Function Multiply() As Integer

        Return 10000

    End Function

End Class

Class HundredThousands

    Inherits Terminals

    Public Overrides Function OneStrings() As String

        Return "C|"

    End Function

    Public Overrides Function FourStrings() As String

        Return "CD|"

    End Function

    Public Overrides Function FiveStrings() As String

        Return "D|"

    End Function

    Public Overrides Function NineStrings() As String

        Return "CM|"

    End Function

    Public Overrides Function Multiply() As Integer

        Return 100000

    End Function

End Class

Public Class ParseDecimalToRoman

    Inherits RomanExpression

    Private AllExpressions As New List(Of RomanExpression)() _
       From { _
       New HundredThousands(), _
       New TenThousands(), _
       New Thousands(), _
       New Hundreds(), _
       New Tens(), _
       New Ones() _
    }

    Public Overrides Sub Interpret(ByVal value As InputOutput)

        For Each reExp As RomanExpression In AllExpressions

            reExp.Interpret(value)

        Next

    End Sub

End Class