public T Add <T>(T entity) where T : AbstractEntity
 {
     _dbContext.Entry <T>(entity).State = EntityState.Unchanged;
     _dbContext.Set <T>().Add(entity);
     return(entity);
 }
 public virtual IEnumerable <T> GetAll <T>() where T : class
 {
     return(_dbContext.Set <T>());
 }