Cannot access Item Property Sharepoint 2013

Hi,

I have created a webpart which will access some predefined Document Libraries and will access "Secure Coloumn" Property and print it, Below is the Code. it can access property only when i upload file by browsing one by one, but if i use drag and drop option for Multiple file uploads it cannot access the "Secure Coloumn" value, i don't know why is it behaving , its odd isn't it.

SPSecurity.RunWithElevatedPrivileges(delegate()
            {
                using (SPSite siteCol = new SPSite("http://tccdemo:11200/"))
                {
                    using (SPWeb web = siteCol.RootWeb)
                    {
                        SPList memList1 = web.Lists["iCubeDocLib1"];
                        SPList memList2 = web.Lists["iCubeDocLib2"];
                        SPList memList3 = web.Lists["iCubeDocLib3"];
                        for (int i = 0; i < web.Lists.Count; i++)
                        {
                            if (web.Lists[i].Title == memList1.Title || web.Lists[i].Title == memList2.Title || web.Lists[i].Title == memList3.Title)
                            {
                                SPListItemCollection sharedDocList = web.Lists[i].Items;
                                foreach (SPListItem li in sharedDocList)
                                {
                                    String str = li.Properties["Secure"].ToString();
                                    Console.WriteLine(str);
                                }
                            }
                        }
                    }
                }
            });

Any help will be appreciated.

Thanks in advance,

Jung Lee.