/// <summary>
        /// 导出Excel后，杀死Excel进程
        /// </summary>
        /// <param name="app"></param>
        private static void KillProcess(_Excel.Application app)
        {
            IntPtr t = new IntPtr(app.Hwnd);
            int k = 0;
            GetWindowThreadProcessId(t, out k);
            System.Diagnostics.Process p = System.Diagnostics.Process.GetProcessById(k);
            p.Kill();
        }

        [DllImport("User32.dll", CharSet = CharSet.Auto)]
        public static extern int GetWindowThreadProcessId(IntPtr hwnd, out   int ID);

------解决方案--------------------

探讨

在你的程序调用完Excel后写

workbook.Close(false, Missing.Value, Missing.Value);
System.Runtime.InteropServices.Marshal.FinalReleaseComObject(workbook);
xlApp.Quit();
System.Runtime.InteropServices.Marshal.……


------解决方案--------------------

跟你说了文件打开跟这没关系

ThisApplication.Visible=false

才是决定是否显示的地方