Fast Exporting from DataSet to Excel

public static void ExportToExcel(DataSet dataSet, string outputPath)
   {

       System.Type moAppType;
       // if u use excell 2003 and 2007 on same project, make sure true object u loaded.
       moAppType = System.Type.GetTypeFromProgID("Excel.Application.12");

      // xlApp = (Excel.Application)moApp;
       // Create the Excel Application object
       Application excelApp = (Microsoft.Office.Interop.Excel.Application)System.Activator.CreateInstance(moAppType);
       excelApp.DisplayAlerts = false;


       // Create a new Excel Workbook
       Workbook excelWorkbook = excelApp.Workbooks.Add(Type.Missing);

       int sheetIndex = 0;

       // Copy each DataTable
       foreach (System.Data.DataTable dt in dataSet.Tables)
       {

           // Copy the DataTable to an object array
           object[,] rawData = new object[dt.Rows.Count + 1, dt.Columns.Count];

           // Copy the column names to the first row of the object array
           for (int col = 0; col < dt.Columns.Count; col++)
           {
               rawData[0, col] = dt.Columns[col].ColumnName;
           }

           // Copy the values to the object array
           for (int col = 0; col < dt.Columns.Count; col++)
           {
               for (int row = 0; row < dt.Rows.Count; row++)
               {
                   rawData[row + 1, col] = dt.Rows[row].ItemArray[col];
               }
           }

           // Calculate the final column letter
           string finalColLetter = string.Empty;
           string colCharset = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
           int colCharsetLen = colCharset.Length;

           if (dt.Columns.Count > colCharsetLen)
           {
               finalColLetter = colCharset.Substring(
                   (dt.Columns.Count - 1) / colCharsetLen - 1, 1);
           }

           finalColLetter += colCharset.Substring(
                   (dt.Columns.Count - 1) % colCharsetLen, 1);

           // Create a new Sheet
           Worksheet excelSheet = (Worksheet)excelWorkbook.Sheets.Add(
               excelWorkbook.Sheets.get_Item(++sheetIndex),
               Type.Missing, 1, XlSheetType.xlWorksheet);

           excelSheet.Name = dt.TableName;


           // Fast data export to Excel
           string excelRange = string.Format("A1:{0}{1}",
               finalColLetter, dt.Rows.Count + 1);

           excelSheet.get_Range(excelRange, Type.Missing).Value2 = rawData;

           // Mark the first row as BOLD
           ((Range)excelSheet.Rows[1, Type.Missing]).Font.Bold = true;
       }

       // Save and Close the Workbook

       excelWorkbook.SaveAs(outputPath, XlFileFormat.xlExcel12, Type.Missing,
           Type.Missing, Type.Missing, Type.Missing, XlSaveAsAccessMode.xlExclusive,
           Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);
       excelWorkbook.Close(true, Type.Missing, Type.Missing);
       excelWorkbook = null;

       // Release the Application object
       excelApp.Quit();
       excelApp = null;

       // Collect the unreferenced objects
       GC.Collect();
       GC.WaitForPendingFinalizers();

   }

// Create new ExcelFile.
var ef = new ExcelFile();

// Imports all the tables from DataSet to new file.
foreach (DataTable dataTable in dataSet.Tables)
{
    // Add new worksheet to the file.
    var ws = ef.Worksheets.Add(dataTable.TableName);

    // Insert the data from DataTable to the worksheet starting at cell "A1".
    ws.InsertDataTable(dataTable, "A1", true);
}

// Save the file to XLS format.
ef.SaveXls("DataSet.xls");