Question

Is there ever a case where holding the necessary data to create an object and only creating it when is absolutely necessary, is better/more efficient than holding the object itself?

A trivial example:

class Bar
{
    public string Data { get; set; }
}

class Foo
{
    Bar bar;
    readonly string barData;

    public Foo(string barData)
    {
        this.barData = barData;
    }

    public void MaybeCreate(bool create)
    {
        if (create)
        {
            bar = new Bar { Data = barData };
        }
    }

    public Bar Bar { get { return bar; } }
}

Answer 1

It makes sense if the object performs some complex operation on construction, such as allocate system resources.

You have Lazy<T> to help you delay an object’s instantiation. Among other things, it has thread safety built in, if you need it.