C#.Net 釋放Excel COM程序及記憶體

使用Excel COM元件時開啟或寫入資料完後有調用其方法關閉
但仍無法釋放該元件所使用的記憶體及程序，關閉主程式時會另Excel COM元件成為殭屍並鎖住其表單

正確釋放應該是先使用「Marshal.ReleaseComObject」釋放COM元件，接著在透過GC.Collect及GC.WaitForPendingFinalizers釋放記憶體及程序

程式碼如下：

        /// <summary>
        /// Close Excel
        /// </summary>
        private void CloseExcel()
        {
            if (sheet != null)
            {
                Marshal.ReleaseComObject(this.sheet);
                this.sheet = null;
            }

            if (workbook != null)
            {
                //Close workbook
                this.workbook.Close(0);
                Marshal.ReleaseComObject(this.workbook);
                this.workbook = null;
            }

            if (app != null)
            {
                //Close app
                this.app.Quit();
                Marshal.ReleaseComObject(this.app);
                this.app = null;
            }

            GC.Collect();
            GC.WaitForPendingFinalizers();
            GC.Collect();
            GC.WaitForPendingFinalizers();
            MessageBox.Show("Done","Gererate", MessageBoxButtons.OK);
            Process.Start("explorer.exe", CurrentPath);
        }