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Basic information about OLE automation

When you want to use functionality from other applications you have to decide if you want to use early or late binding of object variables.

Early binding
The binding between the object variable and the object takes place when the application is compiled. This results in better performance compared to when the binding takes place when the application is run (late binding). If you want to create an early binding you have to set a reference to the "foreign" object library you want to use. This is done from the VBE by using the menu Tools, References.... When a VBProject has a reference to an object library you can declare specific object variables (e.g. Dim oDoc As Word.Document). This will also make it easier to program the "foreign-objects" since the VBE will display the same programming help regarding properties, methods and events that it displays for the objects belonging to the application you are working from (the VBE has automatically added the reference to this application in advance).

This is a general code example:

Sub OLEAutomationEarlyBinding()
' replace xxx with one of the following:
' Access, Excel, Outlook, PowerPoint or Word

Dim oApp As xxx.Application ' early binding
Dim oDoc As xxx.Document 
' Excel.Workbook, Outlook.MailItem, PowerPoint.Presentation, Word.Document
    On Error Resume Next ' ignore errors
    Set oApp = GetObject(, "xxx.Application") 
    ' reference an existing application instance
    If oApp Is Nothing Then ' no existing application is running
        Set oApp = New xxx.Application ' create a new application instance
    End If
    On Error GoTo 0 ' resume normal error handling
    If oApp Is Nothing Then ' not able to create the application
        MsgBox "The application is not available!", vbExclamation
    End If
    With oApp
        .Visible = True ' make the application object visible
        ' at this point the application is visible
        ' do something depending on the application...
        Set oDoc = .Documents.Open("c:\foldername\filename.doc")
        ' open a document
'        ...
        oDoc.Close True ' close and save the document
        .Quit ' close the application
    End With
    Set oDoc = Nothing ' free memory
    Set oApp = Nothing ' free memory
End Sub

Late binding
The binding between the object variable and the object takes place when the application is run. This results in slower performance compared to when the binding takes place when the application is compiled (early binding). If you don't add a reference to the objectlibrary belonging to the "foreign" application  you have to declare general object variables (e.g. Dim oDoc As Object). This will make it more difficult to program the "foreign-objects" since the VBE will not display the same programming help regarding properties, methods and events that it displays for the objects belonging to the application you are working from.

This is a general code example:

Sub OLEAutomationLateBinding()
' replace xxx with one of the following:
' Access, Excel, Outlook, PowerPoint or Word

Dim oApp As Object ' late binding
Dim oDoc As Object ' late binding
    On Error Resume Next ' ignore errors
    Set oApp = GetObject(, "xxx.Application") 
    ' reference an existing application instance
    If oApp Is Nothing Then ' no existing application is running
        Set oApp = CreateObject("xxx.Application") 
        ' create a new application instance
    End If
    On Error GoTo 0 ' resume normal error handling
    If oApp Is Nothing Then ' not able to create the application
        MsgBox "The application is not available!", vbExclamation
    End If
    With oApp
        .Visible = True ' make the application object visible
        ' at this point the application is visible
        ' do something depending on the application...
        Set oDoc = .Documents.Open("c:\foldername\filename.doc") 
        ' open a document
'        ...
        oDoc.Close True ' close and save the document
        .Quit ' close the application
    End With
    Set oDoc = Nothing ' free memory
    Set oApp = Nothing ' free memory
End Sub

 

 

Document last updated 2000-11-07 12:49:32      Printerfriendly version

User comments:
Ole P. from Norway wrote (2006-11-27 16:11:12 CET):
Re: binding on another PC
There is no special code to put anywhere.
You would probably want to use late binding in your distributed application/solution.
You will have to edit your existing code and replace all references to e.g. Excel with a general object reference, e.g.:
' Dim xlApp As Excel.Application ' early binding
Dim xlApp As Object ' late binding
DiGiMac from Lake Garda, Italy wrote (2006-11-27 15:58:46 CET):
binding on another PC
Hi, I've incorporated the Word-Excel techniques you illustrate elsewhere into a common word template we use for making a header to send a fax from Word.
It puts in the user's name and e-mail and various things in different languages based on choices made on a form ("send an offer in French" or "ask for a quote in German"). Now, thanks to you, it also picks out a ref n° from an excel file and writes the date and customer name in the same file and all without the user even seeing excel. It works really well . . . on my PC.
But when I place the updated *.dot file on our server the new form doesn't work for anyone else. I think it must be because of the need for each user's Word to have references to the Excel library so I ended up on your page about early and late binding but I don't understand where to put the above code. I can probably figure out which type of binding to use on my own by trial and error (how long it takes to load etc.) but I don't understand if I should put the code in a document_open sub or somewhere else.

 

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