c# - Why does the supposedly-saved file not really get saved? -

the following code taken this tutorial create , save excel file c#:

using excel = microsoft.office.interop.excel;  namespace windowsformsappexceltest {     public partial class form1 : form     {         public form1()         {             initializecomponent();         }          private void buttoncreateexcelfile_click(object sender, eventargs e)         {             excel.application xlapp;             excel.workbook xlworkbook;             excel.worksheet xlworksheet;             object misvalue = system.reflection.missing.value;             xlapp = new excel.application();             xlworkbook = xlapp.workbooks.add(misvalue);             xlworksheet = (excel.worksheet)xlworkbook.worksheets.get_item(1);             xlworksheet.cells[1, 1] = "http://csharp.net-informations.com";             xlworkbook.saveas("csharp-excel.xls",                 excel.xlfileformat.xlworkbooknormal, misvalue, misvalue, misvalue, misvalue,                 excel.xlsaveasaccessmode.xlexclusive, misvalue, misvalue, misvalue, misvalue, misvalue);             xlworkbook.close(true, misvalue, misvalue);             xlapp.quit();              releaseobject(xlworksheet);             releaseobject(xlworkbook);             releaseobject(xlapp);             messagebox.show("excel file created , can find file c:\\csharp-excel.xls");          }          private void releaseobject(object obj)         {             try             {                 system.runtime.interopservices.marshal.releasecomobject(obj); obj = null;             }             catch (exception ex)             {                 obj = null;                 messagebox.show("exception occured while releasing object " + ex.tostring());             }                         {                 gc.collect();             }         }      } // class } // namespace 

it seems run fine -- see messagebox msg, , can step through no signs of problems. file not saved hard drive, should. why not?

saving specific non-root location (a subfolder) works, e.g. this:

string savefullpath = @"c:\misc\csharpexceltest.xls";     xlworkbook.saveas(savefullpath,         excel.xlfileformat.xlworkbooknormal, misvalue, misvalue, misvalue, misvalue,         excel.xlsaveasaccessmode.xlexclusive, misvalue, misvalue, misvalue, misvalue, misvalue); 

the file indeed saved spot.

apparently problem trying save c/root. attempting explicitly save root, this:

string savefullpath = @"c:\csharpexceltest.xls"; 

...(as opposed providing bare filename) fails ignominiously, telling me:

system.runtime.interopservices.comexception unhandled   helplink=c:\program files (x86)\microsoft office\office12\1033\xlmain11.chm   hresult=-2146827284   message=microsoft office excel cannot access file 'c:'. there several possible reasons:  • file name or path not exist. • file being used program. • workbook trying save has same name open workbook.     . . . 

so: save somewhere other root avoid problem.

update

also, seems being saved "documents library" when not providing folder/full path, , assuming save c:. happened folder morning, , saw file there.