How to attach a set of 'And' filters to a QueryOver query?

My method has a parameter which will determine which column to perform a where filter on, so to make things generic I need to be able to perform some logic on which column I want to perform the where on.

Is it possible to attach a .And clause to a given QueryOver<> query?

public List<..> GetABC(SomeType type)
{
   NHibernateHelper.Session.QueryOver<Blah>()
   .Where(x => x.name = "")
   .开发者_Python百科And(x => x.a)  // if type == SomeType.A   then x.a, otherwise x.b (SomeType.B)
}

How could I do this?

I know when doing a criteria query I could create a criteria and then attach it to the query.

Sure.

var query = NHibernateHelper.Session.QueryOver<Blah>()
                  .Where(x => x.name = "");

if(type == SomeType.A)
{
    query = query.And(x => x.a == ...);
}
else
{
    query = query.And(x => x.b == ... );
}

The query will only be executed after the ".List()"

Update: I don't know if you're refering to something like this (in your comment)

var query = NHibernateHelper.Session.QueryOver<Blah>()
                  .Where(x => x.name = "");


Expression<Func<Blah, bool>> typePredicate = null;


if(type == SomeType.A)
{
    typePredicate = x => x.a == ...;
}
else
{
    typePredicate = x => x.b == ...;
}


query = query.Where(typePredicate);

Or probably you're more interested in something in the likes of Detached queries?

Not sure I completely understand the question ... but something like this?

public List<..> GetABC(SomeType type)
{
   NHibernateHelper.Session.QueryOver<Blah>()
   .Where(x => x.name = "")
   .And(x => typeof(type) == SomeType.A ? x.a : x.b)  
}