c# - Releasing Com Objects -

i having issue excel app staying open in task manager, after clean (or think cleaning up) via code. can point out missing snippet of code below:

private void btnbrowsesquid_click(object sender, eventargs e)          //starting , defining excel references         excel.workbook squidbook = null;         excel.application excelapp = null;         excel.worksheet squidsheet = null;         string squidfilename = txtsquid.text;          //reading information "filenames" tab of squid file windows form         excelapp = new excel.application();         excelapp.visible = true;         squidbook = excelapp.workbooks.open(squidfilename);         squidsheet = squidbook.sheets["filenames"];          //do stuff here excel file          //close open excel app         squidbook.close();         excelapp.quit();         marshal.finalreleasecomobject(squidsheet);         marshal.finalreleasecomobject(squidbook);      } 

do following :

worksheets sheets = excelapp.worksheets;  marshal.releasecomobject(squidsheet); marshal.releasecomobject(squidbook ); marshal.releasecomobject(sheets); squidsheet = null; squidbook = null; sheets = null; gc.collect(); gc.waitforpendingfinalizers(); 

you have release sheets because holding reference doing statement :

squidsheet = squidbook.sheets["filenames"];