// Model
public class Post
{
	public string Id { get; set; }
	public string Title { get; set; }
	// .... other things

	public List<View> Views { get; set; }
}

public class View
{
	public DateTime ViewDate { get; set; }
	public string UserId { get; set; }
}

public class PostPreview
{
	public string Id { get; set; }
	public string Title { get; set; }
	// none of the other things
	public int TotalViews { get; set; }
}

// Service to get a preview
private readonly IMongoCollection<Post> _posts;

public async Task<IList<PostPreview>> GetFrontPage(int limit, int skip)
{
	var result = await _posts.Find(_ => true)
	.Project(p => new PostPreview
	{
		Id = p.Id,
		Title = p.Title,
		TotalViews = p.Views.Count
	})
	.Skip(skip).Limit(limit).ToListAsync();
	return result;
}