在vb.net中读取excel文件会使excel进程挂起

下面的代码工作正常,但似乎让excel.exe的实例在后台运行.我如何正确地关闭这个子？

Private Sub ReadExcel(ByVal childform As Fone_Builder_Delux.frmData,ByVal FileName As String)
    ' In progress
    childform.sampleloaded = False
    Dim xlApp As Excel.Application
    Dim xlWorkBook As Excel.Workbook
    Dim xlWorkSheet As Excel.Worksheet

    xlApp = New Excel.ApplicationClass
    xlWorkBook = xlApp.Workbooks.Open(FileName)
    xlWorkSheet = xlWorkBook.Worksheets(1)
    Dim columnrange = xlWorkSheet.Columns
    Dim therange = xlWorkSheet.UsedRange


    childform.datagridHeaders.Columns.Add("","") ' Super imporant to add a blank column,Could improve this
    For cCnt = 1 To therange.Columns.Count

        Dim Obj = CType(therange.Cells(1,cCnt),Excel.Range)
        childform.datagridSample.Columns.Add(Obj.Value,Obj.Value)
        childform.datagridHeaders.Columns.Add(Obj.Value,Obj.Value)

    Next

    For rCnt = 2 To therange.Rows.Count
        Dim rowArray(therange.Columns.Count) As String
        For cCnt = 1 To therange.Columns.Count

            Dim Obj = CType(therange.Cells(rCnt,Excel.Range)
            Dim celltext As String
            celltext = Obj.Value.ToString
            rowArray((cCnt - 1)) = celltext
            'MsgBox(Obj.Value)

        Next
        childform.datagridSample.Rows.Add(rowArray)
    Next

    AdjustHeaders(childform)
    childform.sampleloaded = True
End Sub

简答：适当地关闭每个项目,然后拨打 FinalReleaseComObject.

GC.Collect()
GC.WaitForPendingFinalizers()

If xlWorkSheet Is nothing Then Marshal.FinalReleaseComObject(xlWorkSheet)
If xlWorkBook Is nothing Then
    xlWorkBook.Close(false,false)
    Marshal.FinalReleaseComObject(xlWorkBook)
End If
xlApp.Quit()
Marshal.FinalReleaseComObject(xlApp)

答案很长：阅读本次answer to another question(整篇文章也很有帮助).