EF无法将表达式转换为sql

Question

It looks like EF is not able to translate the express in the following code, this is the call

Counter lastCounter = unitOfWork.CounterRepository.FindLast(x => x.Div == counter.Div, x => x.Div);

this is the method

    public Counter FindLast(Expression<Func<Counter, bool>> predicate, params Expression<Func<Counter, object>>[] includedProperties)
    {
        IQueryable<Counter> set = context.Set<Counter>().Where(predicate);

        foreach (var includeProperty in includedProperties)
        {
            set = set.Include(includeProperty);
        }
        return set.Last();
    }

Any idea what could be the problem?

Answer 1

It's quite simple, really: Entity Framework just does not support Last(). The reason for this is that in SQL, you also cannot select the last element (ie you have SELECT TOP but don't have SELECT BOTTOM ).

See https://docs.microsoft.com/en-us/dotnet/framework/data/adonet/ef/language-reference/supported-and-unsupported-linq-methods-linq-to-entities