How do I convert a text file with some marker delimiter to a xls or xlsx file?

using Excel = Microsoft.Office.Interop.Excel;


void Save()
{
    //Create an Excel application instance
    Excel.Application excelApp = new Excel.Application();

    //Create an Excel workbook instance and open it from the predefined location
    Excel.Workbook excelWorkBook = excelApp.Workbooks.Add(Type.Missing);
    Excel.Worksheet excelWorkSheet = excelWorkBook.Sheets.Add(Type.Missing);
    excelWorkSheet.Name = "mydata";

    int row = 1;
    int column = 1;
    for // a loop for all the column names
    {
        // row 1 contains column headers
        excelWorkSheet.Cells[row, column] = // text of the column header
        ++column;
    }

    int row = 2;    // leave as 1 if no column headers
    foreach (string str in // the lines of text)
    {
        string[] fields = str.Split(new char[]{ '@', '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries);
        for (column = 0; column < fields.length; ++column)
        {
            excelWorkSheet.Cells[row, column + 1] = fields[column];
        }
        row++;
    }
    excelWorkBook.SaveAs(fileName);
    excelWorkBook.Close();
    excelApp.Quit();
}