Generic memoize function

gistfile1.cs

public static class FuncExtensions {
    public static Func<TKey, TResult> Memoize<TKey, TResult>(this Func<TKey, TResult> f) {
        return f.Memoize(EqualityComparer<TKey>.Default);
    }

    public static Func<TKey, TResult> Memoize<TKey, TResult>(this Func<TKey, TResult> f, IEqualityComparer<TKey> equalityComparer) {
        var cache = new ConcurrentDictionary<TKey, Lazy<TResult>>(equalityComparer);
        return key => {
            var lazy = cache.GetOrAdd(key, new Lazy<TResult>(() => f(key)));
            return lazy.Value;
        };
    }
}