Query Return - Generic Entity Framework Repository

Question

I have a generic repository and I realized that it is taking too long to return a query with the selection of some columns of my database, the Query() method is as follows:

public IList<T> Query(System.Linq.Expressions.Expression<Func<T, bool>> Where)
    {
        return Entity.AsExpandable().Where(Where).AsQueryable<T>().AsNoTracking<T>().ToList();
    }

If you observe at the end I still use Take(10), but analyzing the code, there is a field called 'source' that shows 17822 records, so regardless of selecting 10 or 1000, it seems to me that it is always bringing all the records, follows image:

My question is whether I’m with some Entity configuration to always have this behavior or my query call is wrong?

Thank you

Leo

Answer 1

Basically your problem is that when you use the skip and take after the toList(), the EF has gone to the comic book, brought all these records, and the skip and take are happening in memory.

I understand you need to make yours take(10), out of the repository, then I suggest the following change in its function:

public IQueryable<T> 
Query(System.Linq.Expressions.Expression<Func<T, bool>> Where)
{
    return Entity.AsExpandable().Where(Where).AsNoTracking<T>();
}

• We removed the .AsQueryable<T>(), for AsNoTracking<T>(), já te retornaQueryable(T)`. this already helps you a little bit of the performance.
• We removed the ToList(), so that the EF does not go to the database at this very moment, we are just creating its Query, which will be returned. So you would make use of the Query as follows:

---

var resultadoDaQuery = Query(seyWhere).Skip(skipRows).Take(pageSize).ToList();

• At present, when we use the method ToList(), the EF goes to the database, bringing only the records, considering your Skip() and Take().