QueryOver: compare integer values from subqueries

Question

I have to subqueries which both select an integer value:

QueryOver<Type> sq1 = QueryOver.Of<Type>().Where(someCondition)
                                          .Select(x => x.IntegerValue);
QueryOver<Type> sq2 = QueryOver.Of<Type>().Where(somethingElse)
                                          .Select(x => x.IntegerValue);

and want to Compare their results in my main query:

mainQuery.Where(Restrictions.Disjunction().Add(Subqueries.WhereValue(sq1).Le(sq2));

After adding this restriction calling mainQuery.List will result in an error where it tells me that some property does not implement IConvertible, so it seems like it won´t recognize sq1 and sq2 as int values:

"parameter value could not be converted from QueryOver`2 to Int32 (or smth similar)"

Answer 1

The idea / draft of how to achieve that should be like this:

var sq1 = QueryOver.Of<Type>()... // we must be sure that only 1 ROW is returned
var sq2 = QueryOver.Of<Type>()... // because it will be treated as a value

// let's create IProjection
var left  = Projections.SubQuery(sq1.DetachedCriteria);
var right = Projections.SubQuery(sq2.DetachedCriteria);

// the Restriction on top of two projections (we can use SimpleCriteria, but...
// but this Expression can work with two projections... while named LeProperty 
var restriction = Expression.LeProperty(left, right);

and this could be passed into the main query:

mainQuery.Where(restriction);

NOTE: if we use subqueries with <= or > or = ... they must return exactly one row and one column...