Question

    [DataContract]
        [Serializable]
        public class WSAccount
        {
            [DataMember]
            public string AccountNumber { get; set; }
            [DataMember]
            public string Pin { get; set; }        
        }

 [DataContract]
    [Serializable]
    public class WSUser
    {
       [DataMember]
        public WSAccount wsAccount { get; set; }
        [DataMember]
        public bool IsValidUser { get; set; }
    }

Get an error while doing

WSUser user = new WSUser();
 user.wsAccount.AccountNumber = userNameresponse.account.ID;

but resolved when

 WSUser user = new WSUser();
 user.wsAccount = new WSAccount();
 user.wsAccount.AccountNumber = userNameresponse.account.ID;

do i need to instantiate child class WSAccount ??

Answer 1

Yes, you do.

That’s because your default constructor (if not redefined, and it’s not) uses default values for every field or auto-property it has. Meaning, every int gets ‘0’ as a value, and every reference type (wsAccount) – null.

So you do have to instantiate wsAccount property to a correct object, otherwise it’s null.