Blog.cs

public class Blog
{
	public int BlogId { get; set; }
	public string Url { get; set; }

	public List<Post> Posts { get; set; }
}

BloggingContext.cs

public class BloggingContext : DbContext
{
	public DbSet<Blog> Blogs { get; set; }
	public DbSet<Post> Posts { get; set; }

	protected override void OnConfiguring(DbContextOptions builder)
	{
		builder.UseSqlServer(@"Server=(localdb)\v11.0;Database=Blogging;Trusted_Connection=True;MultipleActiveResultSets=True;");
	}

	protected override void OnModelCreating(ModelBuilder builder)
	{
		builder.Entity<Blog>()
			.OneToMany(b => b.Posts, p => p.Blog)
			.ForeignKey(p => p.BlogId);
	}
}

Post.cs

public class Post
{
	public int PostId { get; set; }
	public string Title { get; set; }
	public string Content { get; set; }

	public int BlogId { get; set; }
	public Blog Blog { get; set; }
}