I am getting a null reference exception when I use a class inside of a class

Question

I am using a class that has a member of another class (all of the members are strings), and when I try to set a value I get a null reference exception. Can anyone help me? I'm still kind of new to classes.

Here are my two classes:

    public class MergeFields
    {
        public string FNAME { get; set; }
        public string LNAME { get; set; }
        public string CITY { get; set; }
        public string STATE { get; set; }
    }


    public class Member
    {
        public string email_Address { get; set; }
        public string status { get; set; }
        public MergeFields merge_fields { get; set; }
    }

And here is where I set the value of CITY:

Member Person = new Member();
string cityTest = "New York";
person.merge_fileds.CITY = cityTest; //This is where I get the exception

Am I missing something stupid obvious? Or is this just not possible?

Well, you never set `merge_fields` to anything, so it's null. — Rufus L, May 09 '18 at 16:19
`public MergeFields merge_fields { get; set; } = new MergeFields();` — Rufus L, May 09 '18 at 16:23
This is not a duplicate: this poster is asking why he is getting the error, that is, what is the mistake in his code; the "duplicate" is asking what the error means. — user1074069, May 09 '18 at 16:59

score 2 · Accepted Answer · answered May 09 '18 at 16:19

Yes, you are. You have two choices:

Explicit class initialization:

person.merge_fileds = new MergeFields();

Implicit class initialization:

public class Member
{
   public string email_Address { get; set; }
   public string status { get; set; }
   public MergeFields merge_fields { get; set; }

   public Member(){
      merge_fields = new MergeFields();
   }
}

Using second approach allows you not to change the code for assigning.

score 1 · Answer 2 · answered May 09 '18 at 16:19

1

You neeed to initialize first

person.merge_fileds = new MergeFields{CITY = cityTest};

answered May 09 '18 at 16:19

Harsh

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If you spend more than 5 minutes answering C# questions, you should know that anything to do with a null reference exception is a duplicate... – DavidG May 09 '18 at 16:20
Right, should have done that. Thanks :) – Harsh May 09 '18 at 16:21

I am getting a null reference exception when I use a class inside of a class

2 Answers2