Understanding Linq and orderbydescending

Question

Hey everyone, was wondering if I could get some help.

I'm ordering a list of objects using Linq, which I'm pretty unfamiliar with but it's been going so okay so far. Well it was until I moved some script around.

 myList = myList.OrderByDescending(x => x.GetComponent<CarCheckpoint>().currentprogress).ToList();

I was using the above line of code. I didn't entirely understand how it worked but I assumed that x was the value of the object in the list and by using a simple GetComponent I could grab the value I wanted the order the list by. It was working fine until I moved this script into a new file and attached it to a different object. Before it was part of the object's main script.

 myList = myList.OrderByDescending(x => x.GetComponent<playerposition>().currentprogress).ToList();

So made some slight revisions to the code and this was result. But now it just throws u NullReference exception, so I assume it isn't successfully finding this value.

I've looked around the internet but would still like some light shed on a few things.

Does x represent the items in the list or the object it is attached to?

I am currently trying to grab an int from a script attached to an object inside the list, if the above code is incorrect how instead should I do this?

Sorry to be a pain guys, just this script is giving me a headache. Would really appreciate any clarity on this as the documentation is giving me a headache.

Thanks.

Answer 1

Best Answer

Answer by Matthew A · Mar 31, 2013 at 10:44 AM

x in the lambda expression is an item in the list (a GameObject from the looks of your code).

If you're getting a null reference exception, either your list is null, a GameObject in your list is null (may have been destroyed), or a GameObject doesn't have the correct component attached. You may have to refine your list to weed out possible problems:

 GameObject[] allObjects = GameObject.FindGameObjectsWithTag("Foo"); // or however you're getting the original list...
 
 var goodObjects = allObjects.Where(o => o != null && o.GetComponent() != null);
 
 var result = goodObjects.OrderByDescending(o => o.GetComponent().progress);

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kidshenlong · Mar 31, 2013 at 02:16 PM 0

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Thanks so much for you help. So much more I need to learn! The issue was as you said. I hadn't attached the racer script to every object just 1. Lol late night programming ay? Thanks for your help.

Understanding Linq and orderbydescending

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