Deleting the main database at runtime.

Helo. Iam making an installer/updater for my app that runs on android/standalone. In case of database update to a newer version failes I wont to make a backup of partiali updated database and than delete the original, to create a new database in it's place(to make new app usable to a customer until I manually fix his old database). But when trying to delete a database I get an exception that says that some app(my own) is holding the handle to that file and therefore I cannot delete it. Prior to try{DbDelete("sqliteDatabase.db")} I am calling a dispose dbConnection, reader and other IDisposables. Hre is some code:

          private void DeleteOriginalDatabaseIfCopyExists(string databaseFullFilePath, string backedUpDatabaseFullPath)
     {//DANGER
         if (File.Exists( backedUpDatabaseFullPath))//if abckup was succsessfull...
         {
             Debug.Log("!!!!!!!!!!!!!!!!!!!!! BACKUP !!!!!!!!!!!!!!!!!!:" + backedUpDatabaseFullPath);
             if (File.Exists(databaseFullFilePath))//...and original database stil exists
             {
                 subsidiaryDatabaseInstance.CloseDB();
                 subsidiaryDatabaseInstance = null;
                 GC.Collect();
                 Debug.Log("!!!!!!!!!!!!!!!!!!!!! DELETING ORIGINAL DATABASE !!!!!!!!!!!!!!!!!!:"+ databaseFullFilePath);
                 try
                 {
                     File.Delete(databaseFullFilePath);
                 }
                 catch (Exception ex)
                 {
                     Debug.LogError("!!! Cannot delete the database couse some other program is holding the handle!!! "+ex);
                 }
             }
         }
     }
 
  public void CloseDB()
     {
         try
         {
             if (reader != null)
             {
                 if (!reader.IsClosed)
                     reader.Close(); // this throws an exception
                 reader.Dispose();
                 reader = null;
             }
         }
         catch (Exception ex) { Debug.Log("COULD NOT CLOSE reader.Dispose " + ex); }
         try
         {
             if (dbCommand != null)
                 dbCommand.Dispose();
             dbCommand = null;
         }
         catch (Exception ex) { Debug.Log("COULD NOT CLOSE  dbcmd.Dispose " + ex); }
         try
         {
             if (dbConnection != null)
             {
                 dbConnection.Close();
                 dbConnection.Dispose();
                 dbConnection = null;
             }
             GC.Collect();
         }
         catch (Exception ex) { Debug.Log("COULD NOT CLOSE dbcon.Close " + ex); }
     }
 

what do I do? Am I going wrong about ths?