Releasing COM and quitting Excel32.exe

Thanks BobRodes for that indepth explaination but as I am very new to VB.net I am still having some problems. I released my com object correclty but excel is still running in the background. Any way of shutting it down after releasing my com objects? and in a relate topic. Am I releasing them correctly? Got this from another thread.

Code:

---

Try
    System.Runtime.InteropServices.Marshal.ReleaseComObject(obj)
    obj = Nothing
Catch ex As Exception
    obj = Nothing
Finally
    GC.Collect()
End Try

---

prior to releasing the objects, you need to make sure you .Close your workbook and .Quit the Excel.Application....

Usually the pattern is like this:
release worksheet object
close workboox
release workbook
quit Excel
release Excel

-tg

I have a working example Excel automation properly using objects primer which shows how to properly access objects and dispose of them.

The following code requires a OpenDialog, button and Checkbox. If the CheckBox is unchecked then we access the active worksheet which was the last sheet accessed via opening Excel and selecting a sheet which is not what you really want. If checked you can pass an numeric but suppose you want Sheet1 which has an index of 3 instead of 1? Also xlWorkSheet when passed in a numeric will not release unless calling the GC.

Code:

---

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim InitialPath As String = "C:\DotnetLand2010\Excel1\bin\Debug"

        OpenFileDialog1.Title = "Please select a file to open"
        OpenFileDialog1.FileName = ""

        If IO.Directory.Exists(InitialPath) Then
            OpenFileDialog1.InitialDirectory = InitialPath
        Else
            OpenFileDialog1.InitialDirectory = System.Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments)
        End If

        OpenFileDialog1.Filter = "Excel 2007 (*.xlsx)|*.xlsx|Excel pre 2007|*.xls"

        If OpenFileDialog1.ShowDialog = Windows.Forms.DialogResult.OK Then
            Dim xlApp As Excel.Application = Nothing
            Dim xlWorkBooks As Excel.Workbooks = Nothing
            Dim xlWorkBook As Excel.Workbook = Nothing
            Dim xlWorkSheet As Excel.Worksheet = Nothing
            xlApp = New Excel.Application
            xlApp.DisplayAlerts = False
            xlWorkBooks = xlApp.Workbooks
            xlWorkBook = xlWorkBooks.Open(OpenFileDialog1.FileName)

            xlApp.Visible = False

            If CheckBox1.Checked Then
                xlWorkSheet = CType(xlWorkBook.Sheets(1), Excel.Worksheet)
            Else
                xlWorkSheet = CType(xlWorkBook.ActiveSheet, Excel.Worksheet)
            End If

            Dim xlCells As Excel.Range = Nothing

            Dim xlRangeToRemove = xlWorkSheet.Range("A1:B1")
            Dim MyRange = xlRangeToRemove.EntireColumn
            MyRange.Delete(Nothing)
            xlWorkBook.SaveAs(OpenFileDialog1.FileName, Excel.XlFileFormat.xlOpenXMLWorkbook)
            xlWorkBook.Close()
            xlApp.UserControl = True
            xlApp.Quit()

            If Not MyRange Is Nothing Then
                Marshal.FinalReleaseComObject(MyRange)
                MyRange = Nothing
            End If

            If Not xlRangeToRemove Is Nothing Then
                Marshal.FinalReleaseComObject(xlRangeToRemove)
                xlRangeToRemove = Nothing
            End If
            If Not xlWorkSheet Is Nothing Then
                Marshal.FinalReleaseComObject(xlWorkSheet)
                xlWorkSheet = Nothing
            End If
            If Not xlWorkBook Is Nothing Then
                Marshal.FinalReleaseComObject(xlWorkBook)
                xlWorkBook = Nothing
            End If
            If Not xlWorkBooks Is Nothing Then
                Marshal.FinalReleaseComObject(xlWorkBooks)
                xlWorkBooks = Nothing
            End If
            If Not xlApp Is Nothing Then
                Marshal.FinalReleaseComObject(xlApp)
                xlApp = Nothing
            End If

            If CheckBox1.Checked Then
                GC.Collect()
                GC.WaitForPendingFinalizers()
                GC.Collect()
                GC.WaitForPendingFinalizers()
            End If
            MessageBox.Show("Done")
        End If
    End Sub

---

Another thing, if you use more than one "." this will cause objects not to release.

Wrong

Code:

---

xlWorkSheet.Range("A1").Value

---

Correct

Code:

---

Dim SingleCellToRead = xlWorkSheet.Range("A1")
Dim A1_Value As String = String.Format("A1 = '{0}'", SingleCellToRead.Value)

---

Another link which can help you in interacting with Excel and Cleaning up after you are done. See Point 24 in that link.