HOWTO: Create and Use a Minimal OLE Automation Server

ID: Q129801

The information in this article applies to:

Microsoft Visual Basic Professional and Enterprise Editions, 16-bit and 32-bit, for Windows, version 4.0

SUMMARY

Visual Basic version 4.0 introduces the powerful new ability to create OLE Automation Servers. This article shows you, step by step, how to create a minimal OLE Automation server and use it from a minimal OLE Client. This article does not exercise the full functionality of OLE servers. It is intended to help you write your first OLE Automation Server.

MORE INFORMATION

Phase One - Create the Server

Start a new project in Visual Basic. Form1 is created by default.

From the File menu, choose Remove File to remove Form1.

From the Insert menu, add a Module (Module1) and a Class Module (Class1) to your project.

Type the following code in the General Declarations section of Module1:
```
      Sub Main ()
 
```

NOTE: End Sub will be added automatically for you.

Add the following code to the General Declaration section of Class1:


      Public MyString As String

      Public Function MyFunction() As String
         MyFunction = "You never know what you're gonna get."
      End Function

Add the following code to the Class_Initialize event of Class1:


      Public Sub Class_Initialize()
         MyString = "Life is like a box of chocolates."
      End Sub

In the Properties window for Class1, set the following properties:


   Property      Value
   ------------------------------------
   Instancing    2 - Creatable MultiUse
   Public        True

From the Tools menu, choose Options. In the StartMode group of the Project tab, choose OLE Server. You now have a complete (though limited) OLE automation server. You can choose Make EXE to make an .EXE file that you can run later, or you can choose Make DLL to make an Inprocess OLE Server. Now you're ready to automate your server.

Start the program by choosing Start from the Run menu or by pressing the the F5 key.

Minimize Visual Basic.

Phase Two - Create a Client to Access the Server

Start a second copy of Visual Basic. A new project (Project1) with a default form (Form1) is created.

Add the following code to the appropriate events of Form1:


      ' In the General Declarations section:
      Private MyObj As Object

      Private Sub Form_Load ()
         Set MyObj = CreateObject("Project1.Class1")
      End Sub

      Private Sub Form_Click()
         Print MyObj.MyString
         Print MyObj.MyFunction
      End Sub

      Private Sub Form_Unload (Cancel As Integer)
         Set MyObj = Nothing
      End Sub

Start the program by choosing Start from the Run menu or by pressing the the F5 key.

Click Form1. You'll see this output:

Life is like a box of chocolates.
You never know what you're gonna get.

When Form1 loads, it instantiates one copy of your OLE automation server. On the click, it makes two OLE calls. One to retrieve the value of the MyString public variable and one to invoke the MyFunction public function.

When Form1 unloads, it destroys its created instance of the OLE automation server. If this is the last instance in memory, the server process is removed from memory as well.

Keywords : kbVBp400 IAPOLE VB4WIN
Version : 4.0
Platform : WINDOWS
Issue type :