Disposable singleton in C#

Question

I have a singleton that uses the \"static readonly T Instance = new T();\" pattern. However, I ran into a case where T is disposable, and actually needs to be disposed for u

Answer 1

You could use a nested lazy singleton (See here) with some simple modifications:

public sealed class Singleton : IDisposable
{
    Singleton()
    {
    }

    public static Singleton Instance
    {
        get
        {
            if (!Nested.released)
                return Nested.instance;
            else
                throw new ObjectDisposedException();
        }
    }

    public void Dispose()
    {
         disposed = true;
         // Do release stuff here
    }

    private bool disposed = false;

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

        internal static readonly Singleton instance = new Singleton();
    }
}

Remember to throw ObjectDisposedException in all public methods/properties of the object if it has been disposed.

You should also, provide a finalizer method for the object, in case Dispose doesn't get called. See how to correctly implement IDisposable here.