EvalExtension.cs

public static class EvalExtension
{
    public static TResult Eval<T, TResult>(this T obj, Func<T, TResult> func) where T : class
    {
        return obj.Eval(func, default(TResult));
    }

    public static TResult Eval<T, TResult>(this T obj, Func<T, TResult> func, TResult defaultValue) where T : class
    {
        return obj == null ? defaultValue : func(obj);
    }
}