Question

I recently started using Lazy throughout my application, and I was wondering if there are any obvious negative aspects that I need to take into account when using Lazy<T>?

I am trying to utilize Lazy<T> as often as I deem it appropriate, primarily to help reduce the memory footprint of our loaded, but inactive plugins.

Answer 1

I’ll expand a bit on my comment, which reads:

I’ve just started using Lazy, and find that it’s often indicative
of bad design; or laziness on the part of the programmer. Also, one
disadvantage is that you have to be more vigilant with scoped up
variables, and create proper closures.

For example, I’ve used Lazy<T> to create the pages the user can see in my (sessionless) MVC app. It’s a guiding wizard, so the user might want to go to a random previous step. When the handshake is made, an array of Lazy<Page> objects is crated, and if the user specifies as step, that exact page is evaluated. I find it delivers good performance, but there are some aspects to it that I don’t like, for example many of my foreach constructs now look like this:

foreach(var something in somethings){
     var somethingClosure = something;
     list.Add(new Lazy<Page>(() => new Page(somethingClosure));
} 

I.e. you have to deal with the problem of closures very proactively. Otherwise I don’t think it’s such a bad performance hit to store a lambda and evaluate it when needed.

On the other hand this might be indicative that the programmer is being a Lazy<Programmer>, in the sense that you’d prefer not thinking through your program now, and instead let the proper logic evaluate when needed, as with example in my case – instead of building that array, I could just figure out just what that specific requested page would be; but I chose to be lazy, and do an all in approach.

EDIT

It occurs to me that Lazy<T> also has a few peculiars when working with concurrency. For example there’s a ThreadLocal<T> for some scenarios, and several flag configurations for your particular multi-threaded scenario. You can read more on msdn.