var dlo = new DataLoadOptions();
dlo.LoadWith<Blog>(b => b.Posts);
this.LoadOptions = dlo;

dlo.LoadWith<Blog>(b => b.Posts.Max());

var options = new DataLoadOptions();
options.AssociateWith<Blog>(b =>
    b.Posts.Where(
        p1 => p1.SomeColumn == b.Posts.Max(p2 => p2. SomeColumn)
    ));

var query = from b in context.Blogs
            //probably some where you already have
            select new MyBlogs // or with no type in case it is anonymous
            {
                AColumn = b.AColumn, //map any other values
                LatestPost = b.Posts.Where(
                      p1 => p1.SomeColumn == b.Posts.Max(p2 => p2. SomeColumn)
                  )).ToList()
            }