HOWTO: Create and Use a Minimal ActiveX Component in VB

ID: Q170946

The information in this article applies to:

Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, versions 5.0, 6.0

SUMMARY

Visual Basic versions 5.0 and later feature the ability to create ActiveX Components. This article illustrates how to create a minimal ActiveX Component and use it from a minimal Automation Controller. This article does not exercise the full functionality of ActiveX Components. It is intended to help you write your first ActiveX Component.

MORE INFORMATION

Step One: Create the Server

Start a new project in Visual Basic. Choose either ActiveX EXE or ActiveX DLL.

From the Project Menu, choose Add Module, then Module.

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

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

      End Sub

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


    Property      Value
    ------------------------------------
    Instancing    5 - MultiUse

From the Project menu, choose Project1 Properties. Under the General Tab, choose Sub Main from Startup Object list and click OK.

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

You now have a complete (though limited) OLE automation server. Later, you can choose Make Project1 EXE or Make Project1 DLL from the File menu to create an ActiveX component that can be used without having to run the project. Now you're ready to automate your server.

Minimize Visual Basic.

Step 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 F5 key.

Click Form1. The following text is output to Form1:

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

When Form1 loads, it instantiates one copy of your ActiveX Component. 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 ActiveX Component. If this is the last instance in memory, the server process is removed from memory as well.

REFERENCES

For additional information on creating and using a minimal OLE Automation Server with Visual Basic version 4.0, please see the following article in the Microsoft Knowledge Base:

Q129801 : HOWTO: Create and Use a Minimal OLE Automation Server

Additional query words: OLE Server KBSERVER KBACTIVEX kbVBp500 kbVBp600 kbVBp kbdsd
kbDSupport

Keywords : kbGrpVB
Version :
Platform : WINDOWS
Issue type : kbhowto