Code to Insert data into the Excel File using C# application using Google Code ExcelLibrary
using ExcelLibrary.CompoundDocumentFormat;
using ExcelLibrary.SpreadSheet;
string file = "newdoc.xls";
Workbook workbook = new Workbook();
Worksheet worksheet = new Worksheet("First Sheet");
worksheet.Cells[0, 1] = new Cell((short)1);
worksheet.Cells[2, 0] = new Cell(9999999);
worksheet.Cells[3, 3] = new Cell((decimal)3.45);
worksheet.Cells[2, 2] = new Cell("Text string");
worksheet.Cells[2, 4] = new Cell("Second string");
worksheet.Cells[4, 0] = new Cell(32764.5, "#,##0.00");
worksheet.Cells[5, 1] = new Cell(DateTime.Now, @"YYYY-MM-DD");
worksheet.Cells.ColumnWidth[0, 1] = 3000;
workbook.Worksheets.Add(worksheet); workbook.Save(file);
// open xlsfile
Workbook book = Workbook.Load(file);
Worksheet sheet = book.Worksheets[0];