用子线程调用excel,用尽网上所有释放excel方法...依然无解!!!

窗体一按钮用了个线程
                Thread t1 = new Thread(new ThreadStart(excelOp));
                t1.Start();
线程调用以下方法
excelOp()
{
            Microsoft.Office.Interop.Excel.ApplicationClass excel = new ApplicationClass();
            Workbook wb = excel.Workbooks.Open(@"E:\Book1.xlsx", Type.Missing, Type.Missing,
                Type.Missing, Type.Missing, Type.Missing, Type.Missing,
                Type.Missing, Type.Missing, Type.Missing, Type.Missing,
                Type.Missing, Type.Missing, Type.Missing, Type.Missing);
            .........(一堆处理,只开了workbook,其它啥sheet都不敢用)
            wb.close(false,false,Type.missing);
            System.Runtime.InteropServices.Marshal.ReleaseComObject(wb);
            wb = null;
            excel.Quit();
            System.Runtime.InteropServices.Marshal.ReleaseComObject(excel);
            excel = null;
}
最后在退出窗体的按钮里加个 GC.Collect();
还是不行...崩溃了..
直接写了个方法杀进程没办法了.....
大家再帮看看是不是代码问题
--------------------编程问答-------------------- 进程退出的时候,应该就会释放掉了吧 --------------------编程问答-------------------- wait..

补充：.NET技术 ,  C#