Imports System
Module Program
' 1. Define metadata class
Public Class Metadata
Public Property Name As String
Public Property IsActive As Boolean
End Class
' 2. Define a base class for the variant dimensions (union equivalent)
Public MustInherit Class Dimension
End Class
Public Class Circle
Inherits Dimension
Public Property Radius As Single
End Class
Public Class Rectangle
Inherits Dimension
Public Property Width As Single
Public Property Height As Single
End Class
' 3. Define the main container class holding ID, metadata, and variant dimension
Public Class Shape
Public Property Id As Integer
Public Property Metadata As Metadata
Public Property Dimension As Dimension
End Class
''' <summary>
''' Safely accesses and prints properties from nested classes and variant types
''' using idiomatic VB.NET type-checking patterns.
''' </summary>
Public Sub PrintShapeProperties(shape As Shape)
If shape Is Nothing Then
Console.WriteLine("Error: Received null shape.")
Return
End If
' Accessing nested properties using standard dot syntax
Console.WriteLine($"Shape ID: {shape.Id}")
Console.WriteLine($"Shape Name: {shape.Metadata.Name}")
Console.WriteLine($"Status: {If(shape.Metadata.IsActive, "Active", "Inactive")}")
' Check runtime type and safely cast to access active variant fields
If TypeOf shape.Dimension Is Circle Then
Dim c = DirectCast(shape.Dimension, Circle)
Console.WriteLine("Type: Circle")
Console.WriteLine($"Radius: {c.Radius}")
ElseIf TypeOf shape.Dimension Is Rectangle Then
Dim r = DirectCast(shape.Dimension, Rectangle)
Console.WriteLine("Type: Rectangle")
Console.WriteLine($"Width: {r.Width}, Height: {r.Height}")
End If
Console.WriteLine("------------------------------------")
End Sub
Sub Main(args As String())
' Initialize a Circle shape using object initializers
Dim myCircle As New Shape With {
.Id = 101,
.Metadata = New Metadata With {.Name = "Unit Circle", .IsActive = True},
.Dimension = New Circle With {.Radius = 5.5F}
}
' Initialize a Rectangle shape
Dim myRectangle As New Shape With {
.Id = 102,
.Metadata = New Metadata With {.Name = "Bounding Box", .IsActive = False},
.Dimension = New Rectangle With {.Width = 10.0F, .Height = 20.0F}
}
' Print properties
PrintShapeProperties(myCircle)
PrintShapeProperties(myRectangle)
End Sub
End Module
' run:
'
' Shape ID: 101
' Shape Name: Unit Circle
' Status: Active
' Type: Circle
' Radius: 5.5
' ------------------------------------
' Shape ID: 102
' Shape Name: Bounding Box
' Status: Inactive
' Type: Rectangle
' Width: 10, Height: 20
' ------------------------------------
'
