Need a refresher course on property access...

Question

Hi.

I need help with accessing class properties within a given class.

For example, take the below class:

public partial class Account
    {
        private Profile _profile;
        private Email _email;
        private HostInfo _hostInfo;

        public Profile Profile
        {
            get { return _profile; }
            set { _profile = value; }
        }

        public Email Email
        {
            get { return _email; }
            set { _email = value; }
        }

        public HostInfo HostInfo
        {
            get { return _hostInfo; }
            set { _hostInfo = value; }
        }

In the class "Account" exists a bunch of class properties such as Email or Profile. Now, when I want to access those properties at run-time, I do something like this (for Email):

    _accountRepository = ObjectFactory.GetInstance<IAccountRepository>();
    string username = Cryptography.Decrypt(_webContext.UserNameToVerify, "verify");
    Account account = _accountRepository.GetAccountByUserName(username);

    if(account != null)
    {
        account.Email.IsConfirmed = true;

But, I get "Object reference not set..." for account.Email... Why is that? How do I access Account such that account.Email, account.Profile, and so on returns the correct data for a given AccountId or UserName.

    Here is a method that returns Account:

public Account GetAccountByUserName(string userName)
{
    Account account = null;

    using (MyDataContext dc = _conn.GetContext())
    {
        try
        {
            account = (from a in dc.Accounts
                       where a.UserName == userName
                       select a).FirstOrDefault();
        }
        catch
        {
            //oops
        }
    }

    return account;

}

The above works but when I try:

 account = (from a in dc.Accounts
               join em in dc.Emails on a.AccountId equals em.AccountId
               join p in dc.Profiles on em.AccountId equals p.AccountId
               where a.UserName == userName
               select a).FirstOrDefault();

I am still getting object reference exceptions for my Email and Profile
properties. Is this simply a SQL problem or is there something else I need to be doing to be able to fully access all the properties within my Account class?

Thanks!

Answer 1

Your getting this because Email is another class which has not been assigned yet. What you can do is in your constructor default the properties that link to other classes as new items. For example in your ctor:

public Account()
{
   // Set Defaults
   Email = new Email();
   Profile = new Profile();
   HostInfo = new HostInfo();
}

Then you can set their values as desired.

Answer 2

This looks like a case of handling null values on your properties. You should initialize the Email property to something other than null if you expect to store or query against it, or alter the queries so that they can expect to deal with null values. Also if you get a null value from the database, and your property cannot be set to null, the reverse problem occurs.

Answer 3

Just wanted to add: there is now a shorter form for declaring trivial properties:

public Profile Profile { get; set; }
public Email Email { get; set; }
public HostInfo HostInfo { get; set; }

Answer 4

Are you declaring these properties yourself, or are you trying to indicate something like auto-generated code from like Linq-to-SQL?

If this is auto-generated where the Account table references the Email table, etc., then you probably just need to specify that you want those objects to load as well in the load options:

using (MyDataContext dc = _conn.GetContext())
{
    var options = new DataLoadOptions();
    options.LoadWith<Account>(a => a.Email);
    options.LoadWith<Account>(a => a.Profile);
    options.LoadWith<Account>(a => a.HostInfo);

    dc.LoadOptions = options;

    try
    {
        account = (from a in dc.Accounts
                   where a.UserName == userName
                   select a).FirstOrDefault();
    }
    catch
    {
        //oops
    }
}