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System.NullReferenceException for Excel.Workbooks.Open (visual Studio

Visual Studio 2003 error message.
Error message prompted "System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.Office.Interop.Excel.Workbooks.Open" while open excel at user's computer (MS XP Service Pack 3, Office 2000).

It work fine at my development computer (NS XP Service Pack 2, Office 2007).

Part of coding:

Imports Microsoft.Office.Interop

Dim App As New Excel.Application
App.Visible = False
App.Application.SheetsInNewWorkbook = 1
Dim Destination As Excel.Workbook = App.Workbooks.Open("C:\Test.xls")

Any help is very much appreciated...

Dirk Haest

Try this:

Dim Destination As NEW Excel.Workbook = App.Workbooks.Open("C:\Test.xls")

Example below with error-handling

Private Sub OpenExcelFileForEditing(ByVal strFilePath As String)
        Dim App As New Excel.Application
        Dim Destination As New Excel.Workbook 
        App.Visible = False
        App.Application.SheetsInNewWorkbook = 1

        'Open the workbook
        Try
            Destination = App.Workbooks.Open("C:\Test.xls")
        Catch ex As Exception
            MsgBox("Exception:  Model import, could not open model Design Table file: C:\Test.xls")
            Return
        End Try
    End Sub

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Miguel Oz

Please check that your client's Office has all the service packs.

By the way if your code is compiled for Office 2007 (version 12.0) then it will not work for Office 2000. The PIA (or com interfaces are different and not compatible)

If you need to support Office 2000, you need to compile your program with the office 2000 object library (version 9.0) meaning changing the excel references to point to the excel 2000 com components.

chwong67

ASKER

Thanks for your prompt respond.
I re-install Miscoroft Office 2000 for Development computer and also intalled Office XP PIAs.
I faced the error message "QueryInterface for interface Excel._Application failed" for 'App.Visible = False' line.

Miguel Oz

Office 2000 (v9) do not use Office xp pia (v10).
Please point to the right version of com references.

Note:
By the way it is not a good idea to install /reinstall Office versions without clearing the registry from the previous Office entries as it may meess up your system. You are better off using a virtual machine (VMware) to do this stuff.

chwong67

ASKER

Kindly advice on the right version of PIA that I can select for Excel.application. Thanks.

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Miguel Oz

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chwong67

ASKER

Thanks for your time. It's working now.