I'm having a problem with the delegate not delegating... I have an object called Tweet that has a string text and an int score. I want to sort the array of tweet objects(twtArray) in order of the score. This is the code I have:
Array.Sort(twtArray, delegate(Tweet twt1, Tweet twt2)
{
return twt1.score.CompareTo(twt2.score); //(twt1.score - twt2.score)
});
and it throws:
System.NullReferenceException: Object reference not set to an instance of an object. at System.Array.FunctorComparer`1.Compare(T x, T y)
Whilst debugging, I noticed that the first comparison works but in the second comparison, twt2 is null. And it can't be null because I definitely have 8 elements in the array. I've tried reversing twt1 and twt2 as well but makes no difference. I also tried making my own comparison method in the Tweet class but again, same thing. Any help would be appreciated!
Also, I dont think this is a duplicate of this question: List.Sort in C#: comparer being called with null object because i tried all the possible solutions from this but it's not working. i've also searched a lot on google :(
Even if you have a Tweet[] with 8 elements some can be null:
Tweet[] twtArray = new Tweet[8]; // all instances are null
You: The Tweet[] is of size 20 and I can see that there are 8 Tweet objects in there (with correct text and score values) in the first line of my code.
So the array's size is 20 but only 8 are initialized? (see above) Array.Sort needs to compare all with all others.
You could prevent it in this way:
Array.Sort(twtArray, delegate(Tweet twt1, Tweet twt2)
{
if(twt1 == null && twt2 == null) return 0;
if(twt1 == null) return -1;
if(twt2 == null) return 1;
return twt1.score.CompareTo(twt2.score);
});
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