Excel Application in vb.net

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On the first time when the application starts it works fine apExcel is Microsoft.Exc
apExcel.Workbooks.Open(strSheetName)
After that apExcel is nothing Object reference not set to an instance of an object.
NullReferenceException was unhandled

Public apExcel As Microsoft.Office.Interop.Excel.Application = DirectCast(CreateObject("Excel.Application"), Microsoft.Office.Interop.Excel.Application)

VB

Public Sub LoadSpreadsheet(ByRef cSheetType As String)

        Dim strSheetName As String
        Dim cYear As String
        Dim nMsgResp As Short
        Dim cSheetName As String

         Call CloseSheet()

        cYear = GetTheSurveyYear()
        cSheetName = "frm" & cSheetType & cYear & ".xls"

        strSheetName = DevelopmentStatus("data") & cSheetName

        If Not IsTheFileHere(strSheetName) Then
            nMsgResp = MsgBox("The template for " & cYear & " does not exist.  It will be created from the default template.", MsgBoxStyle.Information + MsgBoxStyle.OKOnly, cMsgBoxHeader)
            Call CopyDatabaseFromDefault(strSheetName, cSheetType & ".xls", cYear)
        End If
        Call CreateBackup(strSheetName, cSheetType & ".xls", cYear, False)

        apExcel.Workbooks.Open(strSheetName)
                apExcel.WindowState = Microsoft.Office.Interop.Excel.XlWindowState.xlMaximized

               If Val(apExcel.Version) < 9 Then
            nMsgResp = MsgBox("Your version of Excel may not support all features of the OES Forms System.", MsgBoxStyle.OKOnly, cMsgBoxHeader)
        End If

                apExcel.CommandBars.ActiveMenuBar.Controls.Item("File").Controls.Item("Save").Enabled = False

                apExcel.DisplayAlerts = False
                apExcel.Application.Visible = True
        lSheetLoaded = True

End Sub

Posted 18-Jan-12 5:53am

Tony Radu

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**Orcun Iyigun** · Answer 1 · 2012-01-18T06:40:00

Solution 1

Have you used the magic tool Debugger? Set a break point to this method and review your code line by line.

You are having this exception because you have a null value assigned to one of your variables. I am mostly suspicious at you are getting null value at

C#

DevelopmentStatus("data")

Also it is good to check if you are getting values assigned to cSheetType & cYear.

Good luck,
OI

Posted 18-Jan-12 6:40am

Orcun Iyigun

Comments

Tony Radu 18-Jan-12 13:31pm

both have value. should the workbooks be closed that where i found nothing..

Orcun Iyigun 18-Jan-12 13:40pm

What is the value of strShettName in this line apExcel.Workbooks.Open(strSheetName)Although the values are loaded, the path might not be true? You might need some tweaking in the file path.