Question

I’ve got a singleton class like this.

 class UserInteraction
    {
        private CustomerInformation _loginDetails;
        private MusicDetails[] _musicFilesDownloaded;

        private static volatile UserInteraction _interactionObject = null;
        private static object syncRoot = new Object();
        private UserInteraction()
        {

        }
        public static UserInteraction Instance
        {
           get 
            {
                if (_interactionObject == null) 
                {
                 lock (syncRoot) 
                 {
                     if (_interactionObject == null)
                    _interactionObject = new UserInteraction();
                 }
                }

                return _interactionObject;
            }
        }

        public CustomerInformation UserInfo
        {
            get
            {
                return _loginDetails;
            }
            set
            {

                _loginDetails = value;

            }
        }



        public MusicDetails[] FilesDownloaded
        {
            get
            {
                return _musicFilesDownloaded;
            }

            set
            {
                _musicFilesDownloaded= value;

            }
        }

        public void PurgeContents()
        {

        }
        public void SerializeValues()
        {
        }

    }

I can use the following code to access this singleton class

UserInteraction.Instance.UserInfo.CardData = "";

My questions are as follows

1) As you can see I can read/write into UserInfo structure, that means i can any number of copy of UserInfo. Is this against the laws of SingleTon?

2) If this is against the law of Singleton, how can i prohibit the duplication of UserInfo at the same time assign values into it?

Thanks.

Answer 1

No, this is not against the “laws” of Singleton. A singleton guarantees, that you have at most one instance of a certain class. That you can change the members of that class doesn’t matter.
BTW: There are better ways to implement a singleton. See here: http://csharpindepth.com/Articles/General/Singleton.aspx