index.cs

public class GetIdeas_Index: AbstractMultiMapIndexCreationTask<GetIdeas_Index.Result>
{
    public class Result
    {
        public int TenantId { get; set; }
        public int ApplicationId { get; set; }
        public Guid IdeaId { get; set; }
        public string IdeaTitle { get; set; }
        public string CultureTag { get; set; }
        public int StateId { get; set; }
        public string StateTitle { get; set; }
    }

    public GetIdeas_Index()
    {
        AddMap<StateIdea>(states =>
            from p in states
            from state in p.States
            select new
            {
                p.TenantId,
                p.ApplicationId,
                p.CultureTag,
                state.StateId,
                StateTitle = state.Title,
                IdeaTitle = string.Empty
            });

        AddMap<Idea>(ideas =>
            from idea in ideas
            select new
            {
                idea.TenantId,
                idea.ApplicationId,
                CultureTag = string.Empty,
                idea.StateId,
                StateTitle = string.Empty,
                IdeaTitle = idea.Title
            });

        Reduce = results =>
            from r in results
            group r by r.StateId
            into g
            select new
            {
                TenantId = g.Select(p => p.TenantId).FirstOrDefault(),
                ApplicationId = g.Select(p => p.ApplicationId).FirstOrDefault(),
                CultureTag = g.Select(p => p.CultureTag).FirstOrDefault(p => p != string.Empty),
                StateId = g.Key,
                StateTitle = g.Select(p => p.StateTitle).FirstOrDefault(p => p != string.Empty),
                IdeaTitle = g.Select(p => p.IdeaTitle).FirstOrDefault(p => p != string.Empty)
            };
    }
}