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Singleton constructor question

I created a Singleton class in C # with a public property that I want to initialize the first time I call the Singleton.

This is the code I wrote:

public class BL
{
    private ISessionFactory _sessionFactory;
    public ISessionFactory SessionFactory
    {
        get { return _sessionFactory; }
        set { _sessionFactory = value; }
    }

    private BL()
    {
        SessionFactory = Dal.SessionFactory.CreateSessionFactory();
    }

    private object thisLock = new object();

    private BL _instance = null;
    public BL Instance
    {
        get
        {
            lock (thisLock)
            {
                if (_instance == null)
                {
                    _instance = new BL();
                }
                return _instance;
            }
        }
    }
}

As far as I know, when I first reference the BL instance object in the BL class, it has to load the constructor and initialize the SessionFactory object.

But when I try: BL.Instance.SessionFactory.OpenSession (); I am getting Null Reference Exception and see that SessionFactory is null ...

why?

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1 answer


This is not a singleton. You should link to the excellent guide to singletons in C # . For example, use this pattern:

public sealed class Singleton
{
    static readonly Singleton instance=new Singleton();

    // Explicit static constructor to tell C# compiler
    // not to mark type as beforefieldinit
    static Singleton()
    {
    }

    Singleton()
    {
    }

    public static Singleton Instance
    {
        get
        {
            return instance;
        }
    }
}


Note in particular that the instance is static.

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