public class Invoker<TIn, TOut>
{
    private readonly Func<TIn, TOut> _method;
    private readonly TIn _defaultParameter;

    public Invoker(Func<TIn, TOut> method, TIn defaultParameter = default(TIn))
    {
        this._method = method;
        this._defaultParameter = defaultParameter;
    }

    public TOut Invoke()
    {
        return this.Invoke(this._defaultParameter);
    }

    public TOut Invoke(TIn parameter)
    {
        return this._method(parameter);
    }
}