关闭EXCEL进程

//导入Windows类库，可以获得进程ID
        [DllImport("User32.dll", CharSet = CharSet.Auto)]
        public static extern int GetWindowsThreadProcesId( IntPtr bwnd,out int ID );

/// <summary>
        /// 从Excel 获取学生数据
        /// </summary>
        /// <param name="filePath">带完整路径的Excel文件名</param>
        /// <param name="sheetName">工作表名字</param>
        /// <returns>学生实体集合</returns>
        public List<Student> GetStudentsFromExcel(string filePath, string sheetName)
        {

List<Student> students = new List<Student>();
            Microsoft.Office.Interop.Excel.Application excel =
                new Microsoft.Office.Interop.Excel.Application();
            Worksheet sheet = null;
            Range rNo = null;
            try
            {
                excel.Workbooks.Open(filePath);//打开Excel 文件

foreach (Worksheet wsheet in excel.ActiveWorkbook.Sheets)
                {
                    if (wsheet.Name == sheetName)
                    {
                        sheet = wsheet;
                        break;
                    }
                }
                //读取单元格数据
                if (sheet != null)
                {
                    int row = 2;//当前行号
                    while (true)
                    {
                        //如果碰到学号为空的行，则停止读取数据
                         rNo = sheet.Cells[row, 1] as Range;
                        if (rNo.Text.ToString().Trim().Length == 0)
                        {
                            break;
                        }

Student stu = new Student();
                        //学号
                        Range rContent = sheet.Cells[row, 1] as Range;
                        stu.StudentNo = Convert.ToInt32(rContent.Text.ToString().Trim());
                        //密码
                        rContent = sheet.Cells[row, 2] as Range;
                        stu.LoginPwd = rContent.Text.ToString().Trim();
                        //姓名
                        rContent = sheet.Cells[row, 3] as Range;
                        stu.StudentName = rContent.Text.ToString().Trim();
                        //性别
                        rContent = sheet.Cells[row, 4] as Range;
                        stu.Gender = rContent.Text.ToString().Trim() == "男" ? true : false;
                        //年级
                        rContent = sheet.Cells[row, 5] as Range;
                        stu.GradeId = new GradeManager().GetGradeId(rContent.Text.ToString().Trim());
                        //电话
                        rContent = sheet.Cells[row, 6] as Range;
                        stu.Phone = rContent.Text.ToString().Trim();
                        //地址
                        rContent = sheet.Cells[row, 7] as Range;
                        stu.Address = rContent.Text.ToString().Trim();
                        //出生年月日
                        rContent = sheet.Cells[row, 8] as Range;
                        stu.BornDate = Convert.ToDateTime(rContent.Text.ToString().Trim());
                        //邮箱
                        rContent = sheet.Cells[row, 9] as Range;
                        stu.Email = rContent.Text.ToString().Trim();
                        //身份证号
                        rContent = sheet.Cells[row, 10] as Range;
                        stu.IdentityCard = rContent.Text.ToString().Trim();

students.Add(stu);
                        row += 1;
                    }
                }
                excel.Visible = true;
                //关闭WorkBook
                excel.ActiveWorkbook.Close();
                //关闭Excel
                excel.Quit();
            }
            finally
            {
                ////主动释放COM对象
                //Marshal.ReleaseComObject(sheet);
                //Marshal.ReleaseComObject(excel);
                //Marshal.ReleaseComObject(rNo);
                ////对象引用设置null
                // sheet = null;
                // excel = null;
                // rNo = null;
                ////通过垃圾收集器回收对象
                // GC.Collect();
                //通过Hwnd 获得当前Excel Application对象的句柄对象
                IntPtr t = new IntPtr(excel.Hwnd);
                int k = 0;
                //调用方法获取进程ID
                GetWindowsThreadProcesId(t,out k);
                //由进程ID获取进程
                Process p = Process.GetProcessById(k);
                p.Kill();//关闭进程
            }
            return students;
        }