C# 從server下載檔案

            string fileName = @"D:\app123.apk";
            Response.Clear();
            Response.AddHeader("content-disposition", "attachment;filename=app123.apk");
            Response.ContentType = @"application/octet-stream";
            System.IO.FileStream downloadFile =
                new System.IO.FileStream(fileName, System.IO.FileMode.Open);
            downloadFile.Close();
            Response.WriteFile(fileName);
            Response.Flush();
            Response.End();