asp.net - For Loop in C# not looping -

i have issue loop doesn't loop. i've posted simplified version of code below. basically, using npoi excel library, have excel file data on first , second sheet, need loop through both sheets.

below have done far, works through first sheet , exits. fails increment variable w. can see, there other loops implemented in code function fine don't it.

it's been long day , perhaps i'm missing simple. have placed wrong or something. if else can spot might doing wrong i'd grateful :)

public class salesfileprocessor : isalesprocessor     {         public list<ftpsalesrow> processsalesfile(string filename)         {             try             {              using (filestream fs = file.open(filename, filemode.open, fileaccess.read))             {                 int numberofsheets = 2; //loop through sheets - not work                 (int w = 0; w <= numberofsheets; w++)                 {                     hssfworkbook templateworkbook = new hssfworkbook(fs);                      hssfsheet sheet = templateworkbook.getsheetat(w);                     hssfrow row = null;                       (int = 1; <= sheet.lastrownum; i++)                     {                         ftpsalesdetails t = null;                         int currentcolumn = 0;                          try                         {                             modelcontainer ctn = new modelcontainer();                              row = sheet.getrow(i);                              if (row == null)                             {                                 continue;                             }                              t = new ftpsalesdetails                             {                                 rownumber = i,                                 invoicedate = getcellvalue(row.getcell(0)),                                 countrysoldin = getcellvalue(row.getcell(1)),                                 netunitssold = getcellvalue(row.getcell(2)),                                 item = getcellvalue(row.getcell(3)),                                 productcode = getcellvalue(row.getcell(5)),                             };                              if (t.productcode == null && t.netunitssold == null)                             {                                 return null;                             }                              int qty = int.parse(t.netunitssold);                               (int x = 0; x < qty; x++)                             {                                 itemsale ts = new itemsale                                 {                                     itemid = getitemid(t.productcode),                                     manufacturerid = getmanufacturerid("samsung"),                                     datesold = datetime.now,                                 };                                  ctn.addtoitemsales(ts);                                 ctn.savechanges();                             }                         }                         catch (indexoutofrangeexception) { }                     }                 } //end loop - 1 doesn't work             }         }         catch (ioexception exp)         {             throw new ftpsalesfileprocessingexception("could not open sales data file", exp);         }         catch (exception exp)         {             throw new ftpsalesfileprocessingexception("an unknown eror occured during processing file", exp);         }          return null;     } 

 if (t.productcode == null && t.netunitssold == null)   {       return null;   } 

i'm going guess being hit, causing entire function exit. if trying exit out of iteration of loop try break; instead, or continue mike m pointed out in comments.