I'm giving you the code about export to excel i.e., now i'm 
taking table from database and binding to excel sheet.That 
Excel sheel is on my Local System.
Here i'm using Aspose(its a 3rd Party Tool)
Aspose reduces the code by setting data ,cells etc in Excel 
Sheet.
Its a WebApplication.U can change it to Windows Application.

This code is for Setting the format for Excel Sheet:
public Workbook ExportToExcel(DataSet objDs, string 
strHeader)
        {
            DataTable dtResult;
            dtResult = objDs.Tables[0];

            Workbook excel = new Workbook();
            excel.Worksheets[0].Name = strHeader;

            #region SettingHeaderInformation

            excel.Worksheets[0].Cells
["B4"].Style.Font.IsBold = true;
            excel.Worksheets[0].Cells["B4"].Style.Font.Size 
= 12;
            excel.Worksheets[0].Cells["B4"].PutValue
(strHeader);

            excel.Worksheets[0].Cells
["D4"].Style.Font.IsItalic = true;
            excel.Worksheets[0].Cells["D4"].PutValue
("Dated: " + DateTime.Now.ToLongDateString());

            #endregion

            //Exports data set into excel cells
            Aspose.Cells.Cells exportCells = 
excel.Worksheets[0].Cells;
            exportCells.ImportDataTable(dtResult, false, 5, 
0);

            //This block is to header for exported data 
table.
            Aspose.Cells.Cells sheetCell = excel.Worksheets
[0].Cells;
            for (int i = 0; i < dtResult.Columns.Count; i++)
            {
                if (i != (objDs.Tables[0].Columns.Count - 
1))
                    excel.Worksheets[0].AutoFitColumn(i);

                excel.Worksheets[0].Cells[5, 
i].Style.Number = 49;
                excel.Worksheets[0].Cells[5, 
i].Style.Pattern = BackgroundType.Solid;
                excel.Worksheets[0].Cells[5, 
i].Style.ForegroundColor = excel.GetMatchingColor
(Color.FromName(SystemColors.InactiveCaption.Name));
                excel.Worksheets[0].Cells[5, 
i].Style.Font.IsBold = true;
                excel.Worksheets[0].Cells[5, 
i].Style.Font.Color = Color.White;
                string headerTxt = dtResult.Columns
[i].ColumnName;
                if (headerTxt.Contains(strDesc))
                    headerTxt = headerTxt.Remove
(headerTxt.IndexOf(strDesc));
                else if (headerTxt.Contains(strDesc))
                    headerTxt = headerTxt.Remove
(headerTxt.IndexOf(strDesc));
                excel.Worksheets[0].Cells[5, i].PutValue
(headerTxt);
                if (i < objDs.Tables[0].Columns.Count)
                    excel.Worksheets[0].Cells[5, 
i].Style.HorizontalAlignment = TextAlignmentType.Left;
                else
                    excel.Worksheets[0].Cells[5, 
i].Style.HorizontalAlignment = TextAlignmentType.Right;
            }

            return excel;
        }


In Button we can write this code(its for binding the data 
from database to Excel Sheet):

 protected void Button2_Click(object sender, EventArgs e)
    {
        Aspose.Cells.Workbook workBook = new 
Aspose.Cells.Workbook();
        ExportMethods objExpMethods = new ExportMethods();
        ds = objclass.getpagebal();//calling function from 
businesslayer(table)
        workBook = objExpMethods.ExportToExcel
(ds, "shanti_emp");//shanti_emp is a table name
        workBook.Save("shantiExcel.xls", 
FileFormatType.Default, 
Aspose.Cells.SaveType.OpenInBrowser, Response);
    }

U can convert it according to your convineince.