Unity C# NullReferenceException [duplicate]

Answer 1

any object can be null...

just check your code:

GetComponent<GameManager>();

can give you no GameManager,

questions.ToList<Question>();

or your list is not initialized. Fix it with:

 unansweredQuestions = new List<Question>();

You need to debug your code directly, or just check to != null

Answer 2

There are multiple things going on:

1. (Why are you setting score to 0 if score == 0? You could just leave the else away.)

2. In DisplayScore you are accessing the scoreText field. That will throw a NullReferenceException if you haven't set it in the inspector.

3. In ResetScore you are getting the GameManager instance. The call to ResetQuestions will throw a NullReferenceException if your gameobject that contains the Score script doesn't contain the GameManager script too.

4. In Start of the GameManager you could get a NullReferenceException if you haven't set any question in the inspector.

5. You have an off by one error in your SetCurrentQuestion. Basically if there are no questions you are getting a random number from 0 to 0. The only valid result is 0 in that situation. You are then accessing question with index 0. But there won't be one. (That would throw an IndexOutOfRangeException)

6. Any of your private [SerializeField] fields could throw a NullReferenceException if it hasn't been assigned in the inspector.

As you can see, many of your statements could result in a NullReferenceException. We won't be able to actually tell you where the issue is, because it could be in so many places. You are best off by debugging your code and checking where a variable you are trying to access is null.