MapReduce_issue.cs

using (var documentStore = new DocumentStore { Url = "http://localhost:8080" })
{
    documentStore.Initialise();

    using (var session = documentStore.OpenSession())
    {
        //Only add the index if there are not posts in the database, i.e. the 1st time this is run!!
        if (session.Query<Post>().Count() == 0)
        {
            Console.WriteLine("First time usage, creating indexes");

            documentStore.DatabaseCommands.PutIndex("TagCloud",
                                                    new IndexDefinition
                                                    {
                                                        Map = @"from post in docs.Posts                                                                    
                                                        from Tag in post.Tags
                                                        select new { Tag, Count = 1 }",

                                                        Reduce = @"from result in results
                                                        group result by result.Tag into g
                                                        select new { Tag = g.Key, Count = g.Sum(x => (long)x.Count) }"
                                                    });
        }

        session.Store(new Post { Title = "Title 1", Content = "something", PostedAt = RandomDateTime(), Tags = CreateTags("C#", ".NET") });
        session.Store(new Post { Title = "Title 2", Content = "blah blah", PostedAt = RandomDateTime(), Tags = CreateTags("C#", ".NET") });
        session.SaveChanges();

        var tagCloud = session.Query<TagCloud>("TagCloud").WaitForNonStaleResults().ToArray();

        Console.WriteLine("\n\nBEFORE: TagCloud has " + tagCloud.Count() + " items :");
        foreach (var tagCount in tagCloud)
            Console.WriteLine("  " + tagCount);

        session.Store(new Post { Title = "Title 1", Content = "something", PostedAt = RandomDateTime(), Tags = CreateTags("C#", ".NET") });
        session.Store(new Post { Title = "Title 2", Content = "blah blah", PostedAt = RandomDateTime(), Tags = CreateTags("C#", ".NET") });
        session.SaveChanges();

        tagCloud = session.Query<TagCloud>("TagCloud").WaitForNonStaleResults().ToArray();

        Console.WriteLine("\n\nAFTER: TagCloud has " + tagCloud.Count() + " items :");
        foreach (var tagCount in tagCloud)
            Console.WriteLine("  " + tagCount);

    }
}