For Loop in C# not looping

I have an issue with a Loop that doesn't actually loop. I've posted a simplified version of my code below. Basically, using the NPOI excel library, I have an excel file with data on the first and second sheet, so I need to do a loop to get through both sheets.

Below is what I have done so far, however this only works through the first sheet and then exits. It fails to increment the variable w. As you can see, there are other loops implemente开发者_运维技巧d in this code which function fine so I don't get it.

It's been a very long day and perhaps I'm missing something very simple. I could have it placed wrong or something. If anyone else can spot what I might be doing wrong I'd be very 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 - does not work
                for (int w = 0; w <= numberOfSheets; w++)
                {
                    HSSFWorkbook templateWorkbook = new HSSFWorkbook(fs);

                    HSSFSheet sheet = templateWorkbook.GetSheetAt(w);
                    HSSFRow row = null;


                    for (int i = 1; i <= 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);


                            for (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 - the one that doesn't work
            }
        }
        catch (IOException exp)
        {
            throw new FTPSalesFileProcessingException("Could not open the Sales data file", exp);
        }
        catch (Exception exp)
        {
            throw new FTPSalesFileProcessingException("An unknown eror occured during processing the file", exp);
        }

        return null;
    }

---

 if (t.ProductCode == null && t.NetUnitsSold == null)
  {
      return null;
  }

I'm going to guess that this is being hit, causing your entire function to exit. If you are trying to exit out of that iteration of the for loop try a break; instead, or a continue as Mike M pointed out in the comments.

---

For what you say, assuming your variables are all ok that is the loop is not empty... have you checked you're not hiting this line in the first iteration?

if (t.ProductCode == null && t.NetUnitsSold == null)
                            {
                                return null;
                            }

---

Looking at the code, the only obvious thing sticking out to me is:

HSSFSheet sheet = templateWorkbook.GetSheetAt(w);
HSSFRow row = null;

for (int i = 1; i <= sheet.LastRowNum; i++)

I would guess that sheet.LastRowNum either equals 0 or 1.

---

Maybe the indexOutOfRangeException is thrown and thats beacuse you have only one iteration, or instead of <= you sholud use <. Does the sheet numbers start with zero ?