How to assign data to a child class attribute with in a parent class in C#?

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I am trying to assign data to a child class attribute with in a parent class in c#. I am getting object reference not set to instance of object issue.

What I have tried:

My class is as below:

    public class Header
    {
        public string ReferenceNo { get; set; }
    }

    public class Detail
    {
        public string ROLEID { get; set; }
      
    }

    public class GetRoleDetailsResponse
    {
        public Header Header { get; set; }
        public List<Detail> Details { get; set; }
    }

    public class Root
    {
        public GetRoleDetailsResponse GetRoleDetailsResponse { get; set; }
    }

While trying to assign as below, getting null exception:

GetRoleDetailsResponse obj = new GetRoleDetailsResponse();
           obj.objHeader.ReferenceNo = "54654646";

           obj.Details[0].ROLEID="abc";

Posted 26-Apr-21 3:51am

ranio

Updated 26-Apr-21 4:18am

v2

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OriginalGriff · Answer 1 · 2021-04-26T04:18:00

Well yes, of course you are - and thirty seconds with the debugger would have shown you why! Once it compiled, that is (there is no property objHeader in the GetRoleDetailsResponse class)
You create a new instance of the container class GetRoleDetailsResponse but you don't populate either of the fields it contains.
Try adding defaults to your properties:

C#

public class GetRoleDetailsResponse
    {
        public Header Header { get; set; } = new Header();
        public List<Detail> Details { get; set; } = new List<Detail>();
    }

You'll still get an error on the other line because the list is empty so element 0 doesn't exist, but ... I'm sure you can fix that!