Make a multiplication in a SQL

Question

I have to do a search to return a value , I have to do is the sum of multiplying two fields. I have the following code:

internal double TotalRes(long Id)
{
     double total = 0;
     Reserve rAlias = null;
     var query = Session.QueryOver<Item>();
     query = query.JoinAlias(e => e.Reserve, () => rAlias);
     query = query.Where(() => rAlias.Id == Id);
     query = query.Select(Projections.Sum<Item>(acct => acct.Ammount * acct.Wight));
     object result = query.UnderlyingCriteria.UniqueResult();
     if (result != null)
         total = Convert.ToDouble(result);
     return total;
}

It is giving the following error:

the variable 'acct' type 'tem' is referenced in scope '', but it is not set

How can i return this value?

Condenser

Is Projections your class or is it part of nhibernate? (Never used the library) – Cwm

possible duplicate of Expression.Lambda: Variable 'x' of type '' referenced from scope '', but it is not defined – Sola

Its part of nhibernate @ScottChamberlain – Condenser

What happens if you get the Ammount and the Wight from the query and then do the multiplication? My thought is that Projections does not know what acct.Ammount or acct.Wight is. – Gable

Answer 1

Try to do something like this in the mapping, using formula.

Map(c => c.total).formula("(select sum(Ammount * Wight) from acct)");

Hookworm

Answer 2

Try this

Item rItem = null;
var query = Session.QueryOver<Item>(() => rItem);
...
query = query.Select(Projections.Sum(
        Projections.SqlFunction(new VarArgsSQLFunction("(", "*", ")"),
        NHibernateUtil.Double,
        Projections.Property(() => rItem.Ammount),
        Projections.Property(() => rItem.Wight))));

Khanate