Excel 使用 C# Microsoft Interop Excel 在第 144 行后返回 Null

Question

In C#, I've opened an Excel spreadsheet and I am iterating through it. Whenever I get to line 144, the spreadsheet value returns null for every single line following it. Looking at the spreadsheet, it is clearly not null for lines 144 - 250. I tried saving it in different versions but that didn't work. I've tried copying and pasting into a brand new worksheet. Nothing has worked. Here is my code:

        // initiate Excel
        Excel.Application xlApp;
        Excel.Workbook xlWorkBook;
        Excel.Worksheet xlWorkSheet;
        object misValue = System.Reflection.Missing.Value;

        xlApp = new Excel.Application();
        xlWorkBook = xlApp.Workbooks.Open(lblFileName.Text, 0, true, 5, "", "", true, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "\t", false, false, 0, true, 1, 0);
        xlWorkSheet = (Excel.Worksheet)xlWorkBook.Worksheets.get_Item(1);

        //Get the used Range
        Excel.Range usedRange = xlWorkSheet.UsedRange;

        //Iterate the rows in the used range
        string customerNumber;
        string amount;
        int i = 0;
        decimal dAmount = 0;

        bool runProcess = true;
        bool hasHeader = false;
        string cellValue;
        foreach (Excel.Range row in usedRange.Rows)
        {
            i++; 
            // Column 1 is customer number
            // THE FOLLOWING LINE RETURNS NULL STARTING AT ROW 144
            cellValue = row.Cells[i, 1].Value2 == null ? "" : row.Cells[i, 1].Value2.ToString();
            if (!(cellValue.Length >= 5 && cellValue.Length <= 20))
            {
                    MessageBox.Show(cellValue + " Must be between 5 and 20 Characters - File Will Not Be Processed Row#" + i.ToString());
                    runProcess = false;
            }

        }
        // run process
        // release EXCEL

I did try row.Cells[i, 1].Value2, row.Cells[i, 1].Value and row.Cells[i, 1].Text and got the same results for all. I am including "using Excel = Microsoft.Office.Interop.Excel;"

Sample Data from Excel

 4492605768531895  15.95
 4492605768536544  19.95
 4492605768565459  11.95
 4492605739542347  14.95
 4492605768635795  25.95

Answer 1

I think it has something to do with the Range object size. I tried replace the foreach to this and it worked (for me the null was occurring in line 102)

int maxRows = usedRange.Rows.Count;
for (int i=1;i<=maxRows;i++)
{
    // Column 1 is customer number
   // THE FOLLOWING LINE RETURNS NULL STARTING AT ROW 144
   cellValue = xlWorkSheet.Cells[i, 1].Value2 == null ? "" : xlWorkSheet.Cells[i, 1].Value2.ToString();

    if (!(cellValue.Length >= 5 && cellValue.Length <= 20))
    {
        MessageBox.Show(cellValue + " Must be between 5 and 20 Characters - File Will Not Be Processed Row#" + i.ToString());
        runProcess = false;
    }

}