Custom order for LINQ Query

[nfplee]

Is it possible to order a set of data by a custom order? For example I hoped the following would allow me to filter the items within a list and then order it by the position it appears, however the contains works fine but the order by doesn't appear to be supported.

var ids = new List<int> { 2, 3, 4 };

var foo = session.Query<Foo>()
    .Where(x => ids.Contains(x.Id))
    .OrderBy(x => ids.IndexOf(x.Id))
    .ToList();

[nfplee]

I've come up with the following HQL Generator to achieve this:

public class IndexOfHqlGenerator : BaseHqlGeneratorForMethod {
    public IndexOfHqlGenerator() {
        SupportedMethods = [
            ReflectHelper.GetMethodDefinition<IList<int>>(x => x.IndexOf(0)),
            ReflectHelper.GetMethodDefinition<List<int>>(x => x.IndexOf(0))
        ];
    }

    public override HqlTreeNode BuildHql(MethodInfo method, Expression targetObject, ReadOnlyCollection<Expression> arguments, HqlTreeBuilder treeBuilder, IHqlExpressionVisitor visitor) {
        var collection = (IList<int>)((ConstantExpression)targetObject).Value!;
        var value = visitor.Visit(arguments[0]).AsExpression();

        return treeBuilder.Case(
            collection.Select((x, i) => treeBuilder.When(treeBuilder.Equality(value, treeBuilder.Constant(x)), treeBuilder.Constant(i))).ToArray(),
            treeBuilder.Constant(collection.Count)
        );
    }
}

[hazzik]

I would suggest do in memory ordering for this case.