DataTable to Excel

DataTableToExcel.cs

public string DataTableToWorkBook(DataTable dt, string postfix)
        {
            object oMissing = Missing.Value;

            Microsoft.Office.Interop.Excel.Application app;
            Microsoft.Office.Interop.Excel.Workbooks wkBks;
            Microsoft.Office.Interop.Excel.Workbook wkBk;
            Microsoft.Office.Interop.Excel.Sheets wkShts;
            Microsoft.Office.Interop.Excel.Worksheet wkSht;



            string fileLink;
            string filename = Server.MapPath(fileLink = "tmp/" + DateTime.Now.ToFileTime() + "_" + postfix + ".xls");
            FileStream fs = new FileStream(filename, FileMode.Create);
            fs.Close();

            app = new Microsoft.Office.Interop.Excel.Application();
            try
            {
                app.DisplayAlerts = true;
                wkBks = app.Workbooks;
                wkBk = wkBks.Open(filename, 0, false, 5, "", "", true, Microsoft.Office.Interop.Excel.XlPlatform.xlWindows, "\t", false, false, 0, true, 1, 0);

                wkShts = (Microsoft.Office.Interop.Excel.Sheets)wkBk.Sheets;
                wkSht = (Microsoft.Office.Interop.Excel.Worksheet)wkShts.get_Item(1);

                #region Captions
                for (var i = 0; i < dt.Columns.Count; i++)
                {
                    var cell = wkSht.Cells[1, i + 1];
                    cell.Value = dt.Columns[i].Caption;
                }
                #endregion

                #region Data

                for (var r = 0; r < dt.Rows.Count; r++)
                    for (var c = 0; c < dt.Columns.Count; c++)
                    {
                        var cell = wkSht.Cells[r + 2, c + 1];
                        cell.Value = dt.Rows[r][c];
                    }

                #endregion

                app.Visible = true;
                

                wkBk.Close(true, oMissing, oMissing);

                Marshal.ReleaseComObject(wkSht);
                Marshal.ReleaseComObject(wkShts);
                Marshal.ReleaseComObject(wkBk);
                Marshal.ReleaseComObject(wkBks);

            }
            catch { }
            finally
            {
                app.Quit();
                                
                Marshal.ReleaseComObject(app);

                wkSht = null;
                wkBk = null;
                app = null;
                GC.Collect();

            }

            return fileLink;
        }