Understanding The COM Single-Threaded Apartment Part 1

VERSION 5.00
Begin VB.Form FormMain 
   Caption         =   "Form Main"
   ClientHeight    =   3195
   ClientLeft      =   60
   ClientTop       =   345
   ClientWidth     =   4680
   LinkTopic       =   "Form1"
   ScaleHeight     =   3195
   ScaleWidth      =   4680
   StartUpPosition =   3  'Windows Default
   Begin VB.CommandButton Command_DoLengthyFunction 
      Caption         =   "Do Lengthy Function"
      Height          =   495
      Left            =   240
      TabIndex        =   0
      Top             =   480
      Width           =   3975
   End
End
Attribute VB_Name = "FormMain"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Option Explicit
Dim WithEvents SimpleCOMObject1Obj As SimpleCOMObject1
Attribute SimpleCOMObject1Obj.VB_VarHelpID = -1


Private Sub Command_DoLengthyFunction_Click()
  SimpleCOMObject1Obj.DoLengthyFunction 5000
End Sub

Private Sub Form_Load()
  Set SimpleCOMObject1Obj = New SimpleCOMObject1
  
  SimpleCOMObject1Obj.Initialize
End Sub

Private Sub Form_Terminate()
  SimpleCOMObject1Obj.Uninitialize
End Sub

Private Sub SimpleCOMObject1Obj_LengthyFunctionCompleted(ByVal lStatus As Long)
  Dim strMessage As String
  
  strMessage = "Lengthy Function Completed. Status : " & Str$(lStatus)
  
  MsgBox strMessage
End Sub