Task: Set
C#: using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

class Program
{
    static void PrintCollection(IEnumerable<int> x)
    {
        Console.WriteLine(string.Join(" ", x));
    }
    static void Main(string[] args)
    {
        Console.OutputEncoding = Encoding.UTF8;
        Console.WriteLine("Set creation");
        var A = new HashSet<int> { 4, 12, 14, 17, 18, 19, 20 };
        var B = new HashSet<int> { 2, 5, 8, 11, 12, 13, 17, 18, 20 };

        PrintCollection(A);
        PrintCollection(B);

        Console.WriteLine("Test m ∈ S -- \"m is an element in set S\"");
        Console.WriteLine("14 is an element in set A: {0}", A.Contains(14));
        Console.WriteLine("15 is an element in set A: {0}", A.Contains(15));

        Console.WriteLine("A ∪ B -- union; a set of all elements either in set A or in set B.");
        var aUb = A.Union(B);
        PrintCollection(aUb);

        Console.WriteLine("A ∖ B -- difference; a set of all elements in set A, except those in set B.");
        var aDb = A.Except(B);
        PrintCollection(aDb);

        Console.WriteLine("A ⊆ B -- subset; true if every element in set A is also in set B.");
        Console.WriteLine(A.IsSubsetOf(B));
        var C = new HashSet<int> { 14, 17, 18 };
        Console.WriteLine(C.IsSubsetOf(A));

        Console.WriteLine("A = B -- equality; true if every element of set A is in set B and vice versa.");
        Console.WriteLine(A.SetEquals(B));
        var D = new HashSet<int> { 4, 12, 14, 17, 18, 19, 20 };
        Console.WriteLine(A.SetEquals(D));

        Console.WriteLine("If A ⊆ B, but A ≠ B, then A is called a true or proper subset of B, written A ⊂ B or A ⊊ B");
        Console.WriteLine(A.IsProperSubsetOf(B));
        Console.WriteLine(C.IsProperSubsetOf(A));

        Console.WriteLine("Modify a mutable set.  (Add 10 to A; remove 12 from B).");
        A.Add(10);
        B.Remove(12);
        PrintCollection(A);
        PrintCollection(B);

        Console.ReadKey();
    }
}

VB: 





Private Function createSet(t As Variant) As Collection
    Dim x As New Collection
    For Each elem In t
        x.Add elem, elem
    Next elem
    Set createSet = x
End Function
Private Function isElement(s As Variant, x As Collection) As Boolean
    Dim errno As Integer, t As Variant
    On Error GoTo err
    t = x(s)
    isElement = True
    Exit Function
err:
    isElement = False
End Function
Private Function setUnion(A As Collection, B As Collection) As Collection
    Dim x As New Collection
    For Each elem In A
        x.Add elem, elem
    Next elem
    For Each elem In B
        On Error Resume Next 
        x.Add elem, elem
    Next elem
    Set setUnion = x
End Function
Private Function intersection(A As Collection, B As Collection) As Collection
    Dim x As New Collection
    For Each elem In A
        If isElement(elem, B) Then x.Add elem, elem
    Next elem
    For Each elem In B
        If isElement(elem, A) Then
            On Error Resume Next
            x.Add elem, elem
        End If
    Next elem
    Set intersection = x
End Function
Private Function difference(A As Collection, B As Collection) As Collection
    Dim x As New Collection
    For Each elem In A
        If Not isElement(elem, B) Then x.Add elem, elem
    Next elem
    Set difference = x
End Function
Private Function subset(A As Collection, B As Collection) As Boolean
    Dim flag As Boolean
    flag = True
    For Each elem In A
        If Not isElement(elem, B) Then
            flag = False
            Exit For
        End If
    Next elem
    subset = flag
End Function
Private Function equality(A As Collection, B As Collection) As Boolean
    Dim flag As Boolean
    flag = True
    If A.Count = B.Count Then
        For Each elem In A
            If Not isElement(elem, B) Then
                flag = False
                Exit For
            End If
        Next elem
    Else
        flag = False
    End If
    equality = flag
End Function
Private Function properSubset(A As Collection, B As Collection) As Boolean
    Dim flag As Boolean
    flag = True
    If A.Count < B.Count Then
        For Each elem In A
            If Not isElement(elem, B) Then
                flag = False
                Exit For
            End If
        Next elem
    Else
        flag = False
    End If
    properSubset = flag
End Function
Public Sub main()
    
    Dim s As Variant
    Dim A As Collection, B As Collection, C As Collection
    s = [{"Apple","Banana","Pear","Pineapple"}]
    Set A = createSet(s) 
    
    Debug.Print isElement("Apple", A) 
    Debug.Print isElement("Fruit", A) 
    
    s = [{"Fruit","Banana","Pear","Orange"}]
    Set B = createSet(s)
    Set C = setUnion(A, B)
    
    Set C = intersection(A, B)
    
    Set C = difference(A, B)
    
    Debug.Print subset(A, B)
    
    Debug.Print equality(A, B)
    
    Debug.Print properSubset(A, B)
    
    A.Remove "Apple"
    
    A.Remove 1
    
    A.Add "10", "10"
End Sub