c# - Gem Box Spreadsheet msi error -

i have excel manager c# , choose use gem box spreadsheet free

        var ef = new excelfile();         ef = excelfile.load(file_lettura);         excelworksheet ws = ef.worksheets.activeworksheet;          int riga = 13;         string s = (ws.cells["b6"]).tostring();         string[] r = s.split('-');         int c = 0;          while (ws.cells["b"+riga.tostring()].value != null)         {              if (ws.cells["f"+riga.tostring()].value.tostring() != "")             {                 // add row                 dgwfile.rows.add();                  dgwfile.rows[c].cells[0].value = r[0] + "-" + r[1] + "-" + ws.cells["b"+riga.tostring()].value.tostring();                 dgwfile.rows[c].cells[1].value = ws.cells["d" + riga.tostring()].value.tostring() + ws.cells["g" + riga.tostring()].value.tostring() + ws.cells["h" + riga.tostring()].value.tostring() + ws.cells["i" + riga.tostring()].value.tostring();                 dgwfile.rows[c].cells[2].value = ws.cells["f" + riga.tostring()].value.tostring();                 dgwfile.rows[c].cells[3].value = "0";                 c++;             }             riga++;         } 

vs give me problem @ first "if" error :

an unhandled exception of type 'system.nullreferenceexception' occurred.

i think wrong rows first 3 in advance smile | :)

i've tried it

excelfile ef = excelfile.load(file_lettura); excelworksheet ws = ef.worksheets.activeworksheet; 

i don't believe first 3 lines problem, in order 100% sure need specify exception thrown.

nevertheless presume 1 of excelcell's targeting null. try this:

while (ws.cells["b"+riga.tostring()] != null &&        ws.cells["b"+riga.tostring()].value != null) {     if (ws.cells["f"+riga.tostring()] != null &&         ws.cells["f"+riga.tostring()].value != null)         {