Look In code, I don't suppose, that some more explaining than XML comments is needed
Briefly, it has same item working mechanism as e.g. ListBox... and also it 'builtin-cooperates' with listbox. Also added field logical-like operations And, Or, Xor, AndNot, which enables you to compare, or merge etc your string/integer containers...

''' <summary>Container of integer or string values. Do not store chr(0) and chr(1) in items.</summary>
   Public Class StrContainer
     Dim Data As String
     Dim Cnt As Integer
     Dim chr0 As Char = Chr ( 0 ), chr1 As Char = Chr ( 1 )

     Sub New ()
      Data = ""
      Cnt = 0
     End Sub
     ''' <summary>
     ''' Returns actual count of items within strContainer.
     ''' </summary>
     Function Count () As Integer
       Return Cnt
     End Function
     '''<summary>Fill StrContainer with items of listbox.</summary>
     '''<param name="mode">-before mode:clear before fill, 1:adds only new, 2:adds all</param>
     Sub fromListbox (ByVal lb As ListBox , ByVal mode As Integer )
       Dim i , c As Integer , lb_item As String
       If mode < 0 Then
        Data = "" : Cnt = 0 : mode *= - 1
       End If
      c = lb .Items . Count
       If c > 0 Then
         For i = 0 To c - 1
          lb_item = lb .Items . Item (i )
           If (Not Contains (lb_item ) Or (Not mode = 1 )) Then Add (lb_item )
         Next
       End If
     End Sub
     ''' <summary>Copy items to listbox.</summary>
     ''' <param name="mode">-before mode:clear before fill, 1:adds only new, 2:adds all</param>
     Sub toListbox (ByRef lb As ListBox , ByVal mode As Byte )
       Dim i As Integer , sc_item As String
       If mode = 0 Then lb .Items . Clear ()
       If Cnt > 0 Then
         For i = 1 To Cnt
          sc_item = Item (i )
           If (Not lb .Items .Contains (sc_item )) Or (Not mode = 1 ) Then lb .Items . Add (sc_item )
         Next
       End If
     End Sub
     ''' <summary>Fill StrContainer with items of other StrContainer.</summary>
     ''' <param name="mode">-before mode:clear before fill, 1:adds only new, 2:adds all</param>
     Sub fromStrContainer (ByVal sourceSC As StrContainer , ByVal mode As Integer )
       Dim i As Integer , sc_item As String
       If mode < 0 Then
        Data = "" : Cnt = 0 : mode *= - 1
       End If
       If sourceSC . Count > 0 Then
         For i = 1 To sourceSC . Count
          sc_item = sourceSC . Item (i )
           If (Not Contains (sc_item )) Or (Not mode = 1 ) Then Add (sc_item )
         Next
       End If
     End Sub
     ''' <summary>
     ''' Returns left strcontainer extended by new items from right strcontainer. Same as fromStrcontainer(mode 1).
     ''' </summary>
     Public Shared Operator &(ByVal left As StrContainer , ByVal right As StrContainer ) As StrContainer
       Dim i As Integer , sc_item As String , retval As New StrContainer
      retval = left
       If right . Count > 0 Then
         For i = 1 To right . Count
          sc_item = right . Item (i )
           If (Not retval .Contains (sc_item )) Then retval . Add (sc_item )
         Next
       End If
       Return retval
     End Operator
     ''' <summary>
     ''' Returns left strcontainer extended by all items from right strcontainer. Same as fromStrContainer(mode 2).
     ''' </summary>
     Public Shared Operator +(ByVal left As StrContainer , ByVal right As StrContainer ) As StrContainer
       Dim i As Integer , retval As New StrContainer
      retval = left
       If right . Count > 0 Then
         For i = 1 To right . Count
          retval . Add ( right . Item (i ))
         Next
       End If
       Return retval
     End Operator
     ''' <summary>Returns string containing all items of StrContainer separated by 'separator'.</summary>
     Function itemsToString (ByVal separator As String ) As String
       Dim retval As String
       If Cnt = 0 Then
         Return ""
       ElseIf Cnt = 1 Then
         Return Item ( 1 )
       End If
      retval = Replace (Replace ( Left (Data , Len (Data ) - 1 ), chr0 , "" ), chr1 , separator )
       Return retval
     End Function
     ''' <summary>Adds new item.</summary>
     Sub Add (ByVal item As Integer )
      Data &= chr0 & Trim ( Str ( item )) & chr1
      Cnt += 1
     End Sub
     ''' <summary>Adds new item.</summary>
     Sub Add (ByVal item As String )
      Data &= chr0 & item & chr1
      Cnt += 1
     End Sub
     ''' <summary>Returns item at specified index or chr(0) if not found.</summary>
     Function Item (ByVal index As Integer ) As String
       Dim i As Integer , n As Integer = 0 , ende As Integer , retval As String = ""
       If index > Cnt Or index < 1 Then Return chr0
       For i = 0 To Len (Data ) - 1
         If Data (i ) = chr0 Then
          n += 1
           If n = index Then
            ende = InStr (i + 2 , Data , chr1 )
            retval = Mid (Data , i + 2 , ende - i - 2 )
             Return retval
           End If
         End If
       Next
       Return ""
     End Function
     ''' <summary>Clears container.</summary>
     Sub Clear ()
      Cnt = 0
      Data = ""
     End Sub
     ''' <summary>Returns true if container contains item, otherwise false.</summary>
     Function Contains (ByVal item As String ) As Boolean
       If IndexOf ( item ) > 0 Then Return True
       Return False
     End Function
     ''' <summary>Returns true if container contains item, otherwise false.</summary>
     Function Contains (ByVal item As Integer ) As Boolean
       If IndexOf ( Trim ( Str ( item ))) > 0 Then Return True
       Return False
     End Function
     ''' <summary>Deletes item.</summary>
     Sub Delete (ByVal item As String )
       Dim part1 , part2 , needle As String , loc As Integer
      needle = chr0 & item & chr1
       loc = InStr (Data , needle )
       If loc = 0 Then Exit Sub
      part1 = Left (Data , loc - 1 )
      part2 = Right (Data , Len (Data ) - loc - Len (needle ) + 1 )
      Data = part1 & part2
      Cnt -= 1
     End Sub
     ''' <summary>Deletes item.</summary>
     Sub Delete (ByVal item As Integer )
       Call Delete ( Trim ( Str ( item )))
     End Sub
     ''' <summary>Removes item at specified index.</summary>
     Sub RemoveAt (ByVal index As Integer )
       Delete ( Item (index ))
     End Sub
     ''' <summary>Returns index of item, or 0 if not found.</summary>
     Function IndexOf (ByVal item As String ) As Integer
       Dim i , pos As Integer , n As Integer = 0
      pos = InStr (Data , chr0 & item & chr1 )
       If pos = 0 Then Return 0
       For i = pos - 1 To 0 Step - 1
         If Data (i ) = chr0 Then n = n + 1
       Next
       Return n
     End Function
     ''' <summary>Returns index of item, or 0 if not found.</summary>
     Function IndexOf (ByVal item As Integer ) As Integer
       Return IndexOf ( Trim ( Str ( item )))
     End Function
     ''' <summary>
     ''' Returns strcontainer filled only with items beeing in both left and right strcontainers.
     ''' </summary>
     Public Shared Operator And(ByVal left As StrContainer , ByVal right As StrContainer ) As StrContainer
       Dim i As Integer , retval As New StrContainer , item As String
       For i = 1 To left . Count
         item = left . Item (i )
         If right .Contains ( item ) Then retval . Add ( item )
       Next
       Return retval
     End Operator
     ''' <summary>
     ''' Returns strcontainer filled with all items beeing in left or right strcontainer.
     ''' </summary>
     Public Shared Operator Or(ByVal left As StrContainer , ByVal right As StrContainer ) As StrContainer
       Dim i As Integer , retval As New StrContainer , item As String
       For i = 1 To left . Count
         item = left . Item (i )
         If Not retval .Contains ( item ) Then retval . Add ( item )
       Next
       For i = 1 To right . Count
         item = right . Item (i )
         If Not retval .Contains ( item ) Then retval . Add ( item )
       Next
       Return retval
     End Operator
     ''' <summary>
     ''' Returns strcontainer filled with items beeing only in left or only in right strcontainer.
     ''' </summary>
     Public Shared Operator Xor(ByVal left As StrContainer , ByVal right As StrContainer ) As StrContainer
       Dim i As Integer , retval As New StrContainer , item As String
       For i = 1 To left . Count
         item = left . Item (i )
         If Not right .Contains ( item ) Then retval . Add ( item )
       Next
       For i = 1 To right . Count
         item = right . Item (i )
         If Not left .Contains ( item ) Then retval . Add ( item )
       Next
       Return retval
     End Operator
     ''' <summary>
     ''' Returns strcontainer filled with items beeing in left and not in right strcontainer.
     ''' </summary>
     Function AndNot (ByVal left As StrContainer , ByVal right As StrContainer ) As StrContainer
       Dim i As Integer , retval As New StrContainer , item As String
       For i = 1 To left . Count
         item = left . Item (i )
         If Not right .Contains ( item ) Then retval . Add ( item )
       Next
       Return retval
     End Function
   End Class