Excel Merging Working in Local System but not Working in IIS

private void Merge(string strSourceFolder, string strDestinationFile)
        {
            try
            {
                object missing = System.Reflection.Missing.Value;
                Microsoft.Office.Interop.Excel.ApplicationClass ExcelApp = new Microsoft.Office.Interop.Excel.ApplicationClass();
                ExcelApp.Visible = false;
               
                Microsoft.Office.Interop.Excel.Application appExcel = new Microsoft.Office.Interop.Excel.ApplicationClass();
               
                //Create destination object
                Microsoft.Office.Interop.Excel.Workbook objBookDest = ExcelApp.Workbooks.Add(missing);
                objBookDest.UserControl = true;
               
                foreach (string filename in Directory.GetFiles(strSourceFolder))
                {
                    //string filename1;
                    
                    if (File.Exists(filename))
                    {                    
                      
                        Microsoft.Office.Interop.Excel.Workbook objBookSource = ExcelApp.Workbooks._Open
                        (filename, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing
                        ,Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);


                        //Browse through all files.
                        foreach (Microsoft.Office.Interop.Excel.Worksheet sheet in objBookSource.Worksheets)
                        {

                            string Sheetname = sheet.Name.ToLower();
                            //sheet.Name = Sheetname.Substring(1);

                            sheet.Copy(Type.Missing, objBookDest.Worksheets[objBookSource.Worksheets.Count]);
                            objBookSource.Close(Type.Missing, Type.Missing, Type.Missing);
                            objBookSource = null;
                        }

                    }

                }

                foreach (string filename1 in Directory.GetFiles(Server.MapPath("~\\MergeReports\\")))
                {
                    if (File.Exists(filename1))
                    {
                        File.Delete(strDestinationFile);
                        break;
                    }
                }

             


                objBookDest.SaveAs(strDestinationFile, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, myExcel.XlSaveAsAccessMode.xlNoChange, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing);
                 objBookDest.Close(Type.Missing, Type.Missing, Type.Missing);


                objBookDest = null;
                ExcelApp = null;

                string[] filePaths = Directory.GetFiles(Server.MapPath("~\\Merge\\"));
                foreach (string filePath in filePaths)
                    File.Delete(filePath);
            }
            catch (System.Exception e)
            {
                objException = new BaseException(BasePage.GetCurrentUser.UserID.ToString(), e);
            }
        }