Asp.Net MVC，db.Blog.Add（blog）它说这行有错误吗？

Question

我的asp.net模型视图控制器项目的db.Blog.Add（blog）行中有错误！谁能帮我吗？

 public ActionResult GetIndex()
    {
        BlogContext db = new BlogContext();
        Blog blog = new Blog();
        blog.Id = 7;
        blog.Title = "My Asp.Net MVC Blog";
        blog.BloggerName = "My blog name";
        db.Blogs.Add(blog);//My error!
        db.SaveChanges();
        db.Dispose();
        db = null;
        return View();
    }