Generic Singleton

I've no idea why a generic singleton class is not available in the .Net framework, so I had to write my own. Here's the result.

public class Singleton<T> where T : Singleton<T>
{
    private static object instanceLock = new object();
    private static T value;

    public static T Value { get { return GetValue(); } }

    private static T GetValue()
    {
        lock (instanceLock)
        {
            if (value == null)
            {
                value = (T)Activator.CreateInstance(typeof(T), true);
            }
        }
        return value;
    }
}

To use it define a sealed subclass with a private constructor and away you go. For example

public sealed class ContextSingleton : Singleton<ContextSingleton>
{
    private ContextSingleton() { }
}

If you have got a few extra minutes, it might be worth checking to ensure that the subclass is sealed and has no public constructors at runtime in the GetValue() method.