如何结束excel.exe进程？

Dim newWorkBook As Excel.Workbook = app.Workbooks.Open(MyFileName) 

Dim objWorkbooks As Excel.Workbooks = app.Workbooks
Dim newWorkbook As Excel.Workbook = objWorkbooks.Open(MyFileName)
...
Marshal.ReleaseComObject(objWorkbooks)
Marshal.ReleaseComObject(newWorkbook)
...

Sub UsingExcel()

    'declare process; will be used later to attach the Excel process
    Dim XLProc As Process

    'call the sub that will do some work with Excel
    'calling Excel in a separate routine will ensure that it is 
    'out of scope when calling GC.Collect
    'this works better especially in debug mode
    DoOfficeWork(XLProc)

    'Do garbage collection to release the COM pointers
    'http://support.microsoft.com/kb/317109
    GC.Collect()
    GC.WaitForPendingFinalizers()

    'I prefer to have two parachutes when dealing with the Excel process
    'this is the last answer if garbage collection were to fail
    If Not XLProc Is Nothing AndAlso Not XLProc.HasExited Then
        XLProc.Kill()
    End If

End Sub

'http://msdn.microsoft.com/en-us/library/ms633522%28v=vs.85%29.aspx
<System.Runtime.InteropServices.DllImport("user32.dll", SetLastError:=True)> _
    Private Shared Function GetWindowThreadProcessId(ByVal hWnd As IntPtr, _
    ByRef lpdwProcessId As Integer) As Integer
End Function

Private Sub ExcelWork(ByRef XLProc As Process)

    'start the application using late binding
    Dim xlApp As Object = CreateObject("Excel.Application")

    'or use early binding
    'Dim xlApp As Microsoft.Office.Interop.Excel

    'get the window handle
    Dim xlHWND As Integer = xlApp.hwnd

    'this will have the process ID after call to GetWindowThreadProcessId
    Dim ProcIdXL As Integer = 0

    'get the process ID
    GetWindowThreadProcessId(xlHWND, ProcIdXL)

    'get the process
    XLProc = Process.GetProcessById(ProcIdXL)


    'do some work with Excel here using xlApp

    'be sure to save and close all workbooks when done

    'release all objects used (except xlApp) using NAR(x)


    'Quit Excel 
    xlApp.quit()

    'Release
    NAR(xlApp)

End Sub

Private Sub NAR(ByVal o As Object)
    'http://support.microsoft.com/kb/317109
    Try
        While (System.Runtime.InteropServices.Marshal.ReleaseComObject(o) > 0)
        End While
    Catch
    Finally
        o = Nothing
    End Try
End Sub

Quit()

Dim app As New Excel.Application    
Try
    '...
    'After doing your stuff
    '...
    app.Quit()
Catch ex As Exception
    'Log your exception
    System.Diagnostics.Print("Error: " + ex.Message)
End Try