How do I initialize a list of objects

Question

This is my controller fetching a list of blogpost and stores the in listOfBlogposts:

 //BlogHome
        public ActionResult BlogHome(string pageId, string viewName)
        {
            var page = RavenSession.Load<ContentPage>(pageId) as BlogListContentPage;

            var listOfAllBlogPosts =
                RavenSession.Query<ContentPage>().Where(o => o.Template.Action.Equals("SingleBlogPost")).ToList();

            page.SingleBlogPostsContentPages = listOfAllBlogPosts;

            return View(viewName, page);
        }

The class containing the list:

public class BlogListContentPage : ContentPage
{
    public List<ContentPage> SingleBlogPostsContentPages { get; set; }
}

When the debugger comes to this line:

page.SingleBlogPostsContentPages = listOfAllBlogPosts;

I get the error:

Object reference not set to an instance of an object

This is a common error for me and I do not know how to solve it..Maybe its more complicated when you, like ib this example, use inheritance..

Your DB query doesn't appear to be returning a page, are you sure a page with `pageId` exists? — James, Jun 20 '14 at 13:48
Think you misunderstand what I mean, does your database hold a record with the same `pageId` that you are querying for? Or even better, in the debugger is `page` `null` before you reach that line? — James, Jun 20 '14 at 13:50
What happened, just now there were 2 answers, both gor downvoted and dissaperaed..My question got downvoted to..To broad? — user2915962, Jun 20 '14 at 13:50
apparently, page is null; I guess that means it cannot be cast to BlogListContentPage — Dennis_E, Jun 20 '14 at 13:50
@James My database contains a page with the same Id that gets passed as a parameter in the methd. — user2915962, Jun 20 '14 at 13:53
So what needs to be don in order for med to cast it as a blogListContentPage? — user2915962, Jun 20 '14 at 13:59
If you remove the cast, is `page` null? What is the name of the table you are querying? — James, Jun 20 '14 at 14:04
If I remove the cast the Page is not null. It the loads a "regular Contentpage". — user2915962, Jun 20 '14 at 14:11
possible duplicate of [What is a NullReferenceException and how do I fix it?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — 48klocs, Jun 20 '14 at 14:18

score -1 · Answer 1 · answered Jun 20 '14 at 13:54

-1

the list SingleBlogPostsContentPages is null so for that reason the program show Object reference not set to an instance of an object.To avoid this change the class BlogListContentPage to :

public class BlogListContentPage : ContentPage
{
    public BlogListContentPage()
    {
        SingleBlogPostsContentPages = new List<ContentPage>();
    }
    public List<ContentPage> SingleBlogPostsContentPages { get; set; }
}

answered Jun 20 '14 at 13:54

Lamourou abdallah

344
2
12

1

Thank you, I guess my problem occurs earlier in the code..In that I cant cast to a BlogListContentPage – user2915962 Jun 20 '14 at 14:03

How do I initialize a list of objects

1 Answers1