Initializing multiple variable in one statement causes NullReferenceException

Question

I am trying to nest a list of objects in a list; I have tried the following:

Instantiation:

  public static List<PhonePeople> Helpdesk, Admins = new List<PhonePeople>();
  public static List<List<PhonePeople>> PDepartments = 
          new List<List<PhonePeople>>{Helpdesk,Admins};

Attempting to add to the helpdesk list as follows:

 MainWindow.PDepartments[counter].Add(thisPerson);

Error:

"Object reference not set to an instance of an object"

I defined counter to 0 , 0 is the index for helpdesk. Mainwindow is where the static list resides. I believe there is an issue with my List of list's or the way i am adding to it;

whats wrong?

Note that I think it is not direct 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) as it more about declaring multiple variables in single statement. @Mods, consider reading the linked question to help you with debugging this type f exception (now and later). — Alexei Levenkov, Sep 26 '14 at 15:16
Thanks Alexei; Will do this next time, I skimmed the titles but was close minded on "nested lists" instead of all the information involved. — ModS, Sep 26 '14 at 16:20

score 6 · Accepted Answer · answered Sep 26 '14 at 15:01

6

Your line public static List<PhonePeople> Helpdesk, Admins = new List<PhonePeople>(); is only instantiating Admins not HelpDesk

answered Sep 26 '14 at 15:01

Jeffrey Wieder

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Exactly what I was just about to write :-) – Pheonyx Sep 26 '14 at 15:01
Oh! how do you chain these? helpdesk = admins = new list ? Thanks by the way this has been a problem for a while! – ModS Sep 26 '14 at 15:03
2

No, that would point the variables to the same object, you need a separate instance for each object reference, so you need two `new` statements. – Charleh Sep 26 '14 at 15:04
Thanks you guys are the best! :D – ModS Sep 26 '14 at 15:09

Initializing multiple variable in one statement causes NullReferenceException

1 Answers1