I cannot close Excel after using it in VB.net

Question

I cannot close Excel after using it in VB.net

Devon Nullman 100

I use vb.net to grab data from a spreadsheet using a background worker, when the data is finished loading I want to close excel but it leaves excel as a background task. The loading seems fine based on the program behavior. Here is the code:

Private Sub BGWLoadData_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) Handles BGWLoadData.RunWorkerCompleted

LblProgress.Text = ""

TxtQuery.Enabled = True

Label1.Text = "Start Typing:"

'Data loaded, now try to close Excel for real. . . .

xlWorkSheet = Nothing

xlWorkBook.Close()

xlWorkBook = Nothing

xlApp.Quit()

xlApp = Nothing

releaseObject(xlApp)

releaseObject(xlWorkBook)

releaseObject(xlWorkSheet)

End Sub

Private Sub releaseObject(ByVal obj As Object)

If obj Is Nothing Then

Exit Sub

End If

Try

System.Runtime.InteropServices.Marshal.ReleaseComObject(obj)

obj = Nothing

Catch ex As Exception

obj = Nothing

Finally

GC.Collect()

End Try

End Sub

No matter what I try, a background excel task is created

Noor Fatima 85 Reputation points

2026-04-30T10:03:33.82+00:00
“Classic COM cleanup issue. You’re releasing objects after setting them to Nothing, and also calling Quit() before fully releasing worksheet/workbook references.

Try this approach instead:

release xlWorkSheet first, then xlWorkBook, then xlApp

don’t set them to Nothing before Marshal.ReleaseComObject

also make sure there are no hidden references (Range, Cells, etc.)

finally call GC.Collect() twice + GC.WaitForPendingFinalizers()

Usually the leftover Excel process is caused by an undisposed COM reference somewhere in the code path.”

Answer accepted by question author

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Your answer

Noor Fatima 85 Reputation points

2026-04-30T10:03:33.82+00:00

“Classic COM cleanup issue. You’re releasing objects after setting them to Nothing, and also calling Quit() before fully releasing worksheet/workbook references.

Try this approach instead:

release xlWorkSheet first, then xlWorkBook, then xlApp

don’t set them to Nothing before Marshal.ReleaseComObject

also make sure there are no hidden references (Range, Cells, etc.)

finally call GC.Collect() twice + GC.WaitForPendingFinalizers()

Usually the leftover Excel process is caused by an undisposed COM reference somewhere in the code path.”

Answer 1

Excel remains as a background task because the Runtime Callable Wrapper (RCW) for the COM objects is still holding references to Excel. Simply setting variables to Nothing and calling ReleaseComObject once is not always enough.

Use the pattern from the documented resolution: explicitly release each COM object in the correct order, looping ReleaseComObject (or using FinalReleaseComObject in .NET 2.0+), and only then force garbage collection if needed.

Example adapted to VB.NET:

Private Sub NAR(ByVal o As Object)
    Try
        While (System.Runtime.InteropServices.Marshal.ReleaseComObject(o) > 0)
        End While
    Catch
    Finally
        o = Nothing
    End Try
End Sub

Private Sub BGWLoadData_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) _
    Handles BGWLoadData.RunWorkerCompleted

    LblProgress.Text = ""
    TxtQuery.Enabled = True
    Label1.Text = "Start Typing:"

    ' Release in reverse order of creation/use
    NAR(xlWorkSheet)

    xlWorkBook.Close(False)
    NAR(xlWorkBook)

    ' If you have xlWorkBooks collection, release it too
    ' NAR(xlWorkBooks)

    xlApp.Quit()
    NAR(xlApp)

    ' Optional: if Excel still does not exit
    GC.Collect()
    GC.WaitForPendingFinalizers()
End Sub

Key points:

Release every Excel COM object that was created (Application, Workbooks, Workbook, Worksheet, etc.).
Release them in reverse order of creation (child objects first, then parent, then Application).
Use a loop with Marshal.ReleaseComObject (or Marshal.FinalReleaseComObject in .NET 2.0 and later) to ensure all RCW references are released.
Only after all COM objects are released, optionally call GC.Collect() and GC.WaitForPendingFinalizers() if Excel still does not shut down.

Following this pattern causes the Excel process to exit once the last COM reference is released.

References:

Office application does not exit after automation from Visual Studio .NET client

Answer 2

Hello @Devon Nullman ,

Thanks for your question.

You can not close Excel after using it in VB.net because:

releaseObject is called after = Nothing. Once you set xlApp = Nothing, VB.NET forgets where Excel is. Passing it to releaseObject after that is like trying to return something you already threw in the trash, the function receives Nothing and immediately exits without releasing anything.
Wrong order of releasing objects You must release from innermost → outermost: xlWorkSheet first, then xlWorkBook, then xlApp. Releasing in the wrong order leaves dangling COM references.
GC.Collect() alone just starts the cleanup but doesn't wait for it to finish. Excel stays in memory until cleanup is fully completed.

You can refer to following code example:


Private Sub BGWLoadData_RunWorkerCompleted(sender As Object, e As RunWorkerCompletedEventArgs) _
    Handles BGWLoadData.RunWorkerCompleted

    LblProgress.Text = ""
    TxtQuery.Enabled = True
    Label1.Text = "Start Typing:"


    If xlWorkBook IsNot Nothing Then
        xlWorkBook.Close(False)
    End If

    If xlApp IsNot Nothing Then
        xlApp.Quit()
    End If


    releaseObject(xlWorkSheet)
    releaseObject(xlWorkBook)
    releaseObject(xlApp)

    xlWorkSheet = Nothing
    xlWorkBook = Nothing
    xlApp = Nothing

    GC.Collect()
    GC.WaitForPendingFinalizers()
    GC.Collect()

End Sub


Private Sub releaseObject(ByVal obj As Object)

    If obj Is Nothing Then
        Exit Sub
    End If

    Try
        Dim remainingRefs As Integer = System.Runtime.InteropServices.Marshal.ReleaseComObject(obj)
        While remainingRefs > 0
            remainingRefs = System.Runtime.InteropServices.Marshal.ReleaseComObject(obj)
        End While

    Catch ex As Exception
        Console.WriteLine("Error releasing object: " & ex.Message)
    Finally
        obj = Nothing
    End Try

End Sub

I hope this addresses your question. If this response was helpful, please consider following the guidance to provide feedback.

Nancy Vo (WICLOUD CORPORATION) 3,550 Reputation points Microsoft External Staff Moderator

2026-05-05T02:50:32.27+00:00

Hi @Devon Nullman ,
If you're still interested or have any questions, feel free to reach out whenever it works best for you.

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I cannot close Excel after using it in VB.net

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