Common way to kill the Excel process

The code follows:

 1string path = @"D:\\test.xls";
 2            Excel.ApplicationClass app = new Microsoft.Office.Interop.Excel.ApplicationClass();
 3            Excel.Workbooks oWorkBooks = app.Workbooks;
 4            Excel.Workbook oWorkBook = null;
 5
 6            oWorkBook = oWorkBooks.Open(path, Type.Missing, (object)false, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing,
 7                    Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);           
 8
 9            Excel.Sheets sheets = oWorkBook.Sheets;
10            Excel.Worksheet oWorkSheet = (Excel.Worksheet)sheets.get_Item(1);
11            oWorkSheet.get_Range("A1", Type.Missing);
12
13            
14
15            
16            //oWorkBook.Close(Type.Missing, Type.Missing, Type.Missing);
17            
18            //oWorkBooks.Close();
19            NAR(oWorkSheet);
20            NAR(sheets);
21            //NAR(oWorkBook);
22            NAR(oWorkBooks);
23            app.Quit();
24            NAR(app);
25           
26            GC.Collect();

 1public void NAR(object o)
 2        {
 3            try
 4            {
 5                System.Runtime.InteropServices.Marshal.ReleaseComObject(o);
 6            }
 7            catch
 8            {
 9            }
10            finally
11            {
12                o = null;
13            }
14        }

Notice:
Why we needn't release the Worksheet and Workbook COM object? That is we release the Worksheets and Workbooks object, who is the collection of Worksheet and Workbook, so the sub object will be release togother.

When we use the Worksheets and Workbooks object, and have not defiend them, the Excel process will not be killed. So before we use the Worksheets and Workbooks must to declare them! The detail code had been belowed.

Good Luck!