Dynamic ocx into a program

[kmchong]

How can I dynamically register a custom ocx into my program?

If I can, then how to handle for the events and property?

[Chris]

Here the sample from www.AllApi.net"

' Add 2 Commandbuttons and a textbox to the form, and paste this code into the form
Option Explicit

Private Declare Function FreeLibrary Lib "kernel32" (ByVal hLibModule As Long) As Long
Private Declare Function LoadLibrary Lib "kernel32" Alias "LoadLibraryA" (ByVal lpLibFileName As String) As Long
Private Declare Function GetProcAddress Lib "kernel32" (ByVal hModule As Long, ByVal lpProcName As String) As Long
Private Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hWnd As Long, ByVal Msg As Any, ByVal wParam As Any, ByVal lParam As Any) As Long
Private Const ERROR_SUCCESS = &H0

Private Sub Form_Load()
    Text1.Text = "C:\WINDOWS\SYSTEM\COMCTL32.OCX"
    Command1.Caption = "Register server"
    Command2.Caption = "Unregister server"
End Sub

Private Sub Command1_Click()
    Call RegisterServer(Me.hWnd, Text1.Text, True)
End Sub

Private Sub Command2_Click()
    Call RegisterServer(Me.hWnd, Text1.Text, False)
End Sub

Public Function RegisterServer(hWnd As Long, DllServerPath As String, bRegister As Boolean)
    On Error Resume Next

    'KPD-Team 2000
    'URL: http://www.allapi.net/
    'E-Mail: [email protected]
    'We're going to call an API-function, without declaring it!

    ' Modified by G. Kleijer
    ' [email protected]
    ' going to call the DllRegisterServer/DllUnRegisterServer API of the specified library.
    ' there's no need to use the Regsvr32.exe anymore.

    ' Make sure the path is correct and that the file exists, otherwise VB will crash.

    Dim lb As Long, pa As Long
    lb = LoadLibrary(DllServerPath)

    If bRegister Then
        pa = GetProcAddress(lb, "DllRegisterServer")
    Else
        pa = GetProcAddress(lb, "DllUnregisterServer")
    End If

    If CallWindowProc(pa, hWnd, ByVal 0&, ByVal 0&, ByVal 0&) = ERROR_SUCCESS Then
        MsgBox IIf(bRegister = True, "Registration", "Unregistration") + " Successful"
   Else
        MsgBox IIf(bRegister = True, "Registration", "Unregistration") + " Unsuccessful"
    End If
    'unmap the library's address
    FreeLibrary lb
End Function

You can load an unreferenced OCX by using the CreateObject function with the prgrammatic ID:

CreateObject("MSComCtl.TreeView")

As to how to capture the events, well, you need to access the OCX through an interface. If the OCX or DLL is one you've written, no problem, If it's not, then it's going to be far more difficult (you'll probably have to wrap it in another OCX).

You need to create an interface DLL, and make your OCX implement the DLL. The application has a reference to the DLL (but it doesn't need to be dstributed with the application). The interface DLL contains a map of all the functions and events you want to expose, but contains no actual code.

So, in the code where you call the CreateObject function, you neet to put it into an Object variable, then cast the variable to a second variable of the interface type. That way, you can get the events, anmd the whole thing is effectively early-bound (it's actually IDisp type binding, but at least it's not late-bound).

If you want further info, reply to this post, and I'll provide a better description tomorrow (I've got to go home now - well, more like an hour ago).

In the meantime, look through the vbpj.com archives for an article called "Dynamic MDI" or something similar by Francesco Balena. That explains this concept pretty well.

- gaffa