Declaring VB's ActiveX DLL at Runtime - Urgent ??

[omarswan]

Hi,
If I created a ActiveX DLL in VB how can I load it at runtine without refrencing it.


example:

 
Public Declare Function MyHello Lib "PLUGIN.dll" Alias "Hello" (ByVal Name As String) As Long

What would the code in the ActiveX DLL and the program look like.

Please

[Ruxpin]

Placing a reference to a dll when designing your project is called early binding. What you are after is late binding which you can do with CreateObject().

Dim objSomething as object

'Create the object based on the project name and
'class name.
Set objSomething = CreateObject("MyDll.MyObject")

'Call a method
objSomething.DoSomething

[omarswan]

If I knew the path and filename of the DLL file but the DLL file was not registered, how could I create an Object for it.

For example:
In VB if you want to Refrence a DLL file. You could simple go to the Refrences Option and select from the list of already refrenced Objects of you could browse for the file.

How could I write a code that retrieves the information from a DLL file that it can you when you want to use the CreatOBject()

keep in mind that I know the path and filename of the DLL file, I just need to get the information from the DLL file so that I can use the CreateObject Function.

Example

dll_filepath = "c:\mydll.dll"

If I know the path and file name, how do I retrieve the information from the file in order to create an object.


Thanks.


[Edited by omarswan on 06-02-2000 at 04:42 AM]

[Mark Sreeves]

This will populate a list with the classes present in an ActiveX DLL

The class names need to have been included in the resouce file for it to work

Option Explicit
Private Declare Function LoadString Lib "user32" Alias "LoadStringA" (ByVal hInstance As Long, ByVal wID As Long, ByVal lpBuffer As String, ByVal nBufferMax As Long) As Long
Private Declare Function LoadLibrary Lib "kernel32" Alias "LoadLibraryA" (ByVal lpLibFileName As String) As Long
Private Declare Function FreeLibrary Lib "kernel32" (ByVal hLibModule As Long) As Long



Sub FillClassNameList(FileName As String)
    ' Get the list of classnames contined with a component from the components
    ' resource data.
    
    ' Set the error handler
    'On Error GoTo GetClassNameListErr
    Dim ModuleHandle As Long
    Dim ClassNames() As String
    ModuleHandle = LoadLibrary(FileName)


    ' Start by getting the number of classnames
    Dim StringLength As Integer
    Dim Buffer As String
    Dim Length As Long
    Dim NumClassNames As Long
    Length = 255
    Buffer = String(Length, vbNullChar)
    StringLength = LoadString(ModuleHandle, 2, Buffer, Length)
    NumClassNames = Val(Left(Buffer, StringLength))

    ' Create the storage space
    ReDim ClassNames(NumClassNames)

    ' Loop thorugh all the class names adding them to the array
    Dim Counter As Long
    For Counter = 0 To NumClassNames - 1
      Buffer = String(Length, vbNullChar)
      StringLength = LoadString(ModuleHandle, Counter + 3, Buffer, Length)
      'ClassNames(Counter) = Left(Buffer, StringLength)
      List1.AddItem Left(Buffer, StringLength)
    Next Counter

    
    ' Free the module
    FreeLibrary ModuleHandle

  End Sub

[omarswan]

Hi,
Mark thanks for the code but it didn't work when I tried it. What coul I be dooing wrong?

[Mark Sreeves]

omarswan

In what way didn't it work?

[omarswan]

Hi Mark,
this what I did.
1) I created a new exe Project with form1
2) I added a listbox

then...

Option Explicit
Private Declare Function LoadString Lib "user32" Alias "LoadStringA" (ByVal hInstance As Long, ByVal wID As Long, ByVal lpBuffer As String, ByVal nBufferMax As Long) As Long
Private Declare Function LoadLibrary Lib "kernel32" Alias "LoadLibraryA" (ByVal lpLibFileName As String) As Long
Private Declare Function FreeLibrary Lib "kernel32" (ByVal hLibModule As Long) As Long



Sub FillClassNameList(FileName As String)
   ' Get the list of classnames contined with a component from the components
   ' resource data.

   ' Set the error handler
   'On Error GoTo GetClassNameListErr
   Dim ModuleHandle As Long
   Dim ClassNames() As String
   ModuleHandle = LoadLibrary(FileName)


   ' Start by getting the number of classnames
   Dim StringLength As Integer
   Dim Buffer As String
   Dim Length As Long
   Dim NumClassNames As Long
   Length = 255
   Buffer = String(Length, vbNullChar)
   StringLength = LoadString(ModuleHandle, 2, Buffer, Length)
   NumClassNames = Val(Left(Buffer, StringLength))

   ' Create the storage space
   ReDim ClassNames(NumClassNames)

   ' Loop thorugh all the class names adding them to the array
   Dim Counter As Long
   For Counter = 0 To NumClassNames - 1
      Buffer = String(Length, vbNullChar)
      StringLength = LoadString(ModuleHandle, Counter + 3, Buffer, Length)
      'ClassNames(Counter) = Left(Buffer, StringLength)
      List1.AddItem Left(Buffer, StringLength)
   Next Counter


   ' Free the module
   FreeLibrary ModuleHandle

End Sub

Private Sub Form_Load()
  Call FillClassNameList("C:\Omar\MyTemp\vbSendMail.dll")
End Sub

[Mark Sreeves]

The code was taken from a project which consists of lots of small DLLs.

Each DLL has a resource file containing the class names


here's one of the resource file source-files

It was designed by another programmer but it works fine


resource.rc

// The string table
//
// The first entry (number 1) is the file name of the component.
// The second entry (number 2) is the number of class names in the list
// The next set of entries (starting at 3) is a list of all the class
// names in the component
// The remaining entries are application specific
//
// The Components installer looks at the first entries so it can get
// the names of the classes inside the component.
//
STRINGTABLE LOADONCALL MOVEABLE DISCARDABLE 
BEGIN
	1. "INVOIC Formatter.DLL"
	2, "1"
	3, "INVOIC2.Format"
END

using the rc.exe resource compiler you create a .RES file which you then include in your project.

Is this any help to you or do you need a more generic Look-inside-a-dll type of thing? if so repost your original question and I'll just mind my own business.

[Frans C]

You could register the dll first.
For this example I created a dll named testproject1.dll containing a class named testclass1.

Option Explicit
Private Declare Function DllRegisterServer Lib "c:\temp\testproject1.dll" () As Long

Private Sub Command1_Click()
Dim retVal As Long
Dim myClass As Object
    retVal = DllRegisterServer
    Set myClass = CreateObject("testproject1.testclass1")
End Sub