public UnitFactory()
 {
     if (factory == null || factory.Count == 0)
     {
         RepositoryConfiguration  configuration = RepositoryConfiguration.GetConfig();
         RepositoryCollection     col           = configuration.RepositoryCollection;
         IEnumerable <Repository> Repo          = col.Cast <Repository>();
         factory = new Dictionary <string, Type>();
         foreach (Repository item in Repo)
         {
             Type type = Type.GetType(item.DataBase);
             factory.Add(item.RepositoryName, type);
         }
     }
 }