为什么它给我一个 NullReferenceException 但没有错误

Question

创建一个用户可以输入单词的程序，它会弹出一个首字母缩写词，这很容易，但我必须使用字典，并且键必须使我得到的首字母缩写词 NullReferenceException 不明白为什么看不到一个空

仅使用 Visual Studio 2015 我已经尝试了这么多，我的思绪都无法描述，抱歉

    private string fullSentence;
    private string[] words = new string[5];
    private Dictionary<char, string> acronymDictionary = new Dictionary<char, string>();
    public Acronym(string sentence)
    {
        fullSentence = sentence;
        string[] words = sentence.Split(' ');

    }

    public void BuildAcronym()
    {

        char[] key = new char[words.Length];
        //key = null;
        //foreach (string info in words)
        //{
            for (int i = 0; i < words.Length; i++)
            {
                key[i] = Convert.ToChar(words[i].Substring(0,1)); //this is where the problem is
            }

我希望它能够运行，特别是键 chars[] 由 words[] 中每个单词的第一个字母填充，因此我可以将 key[] 设置为字典的键

Answer 1

请试试这个。

    private string fullSentence;
    private string[] words;
    private Dictionary<char, string> acronymDictionary = new Dictionary<char, string>();
    public Acronym(string sentence)
    {
        fullSentence = sentence;
        words = sentence.Split(' ');

    }

    public void BuildAcronym()
    {
        if(words != null)
        { 
        char[] key = new char[words.Length];
        //key = null;
        //foreach (string info in words)
        //{
            for (int i = 0; i < words.Length; i++)
            {
                key[i] = Convert.ToChar(words[i].Substring(0,1)); //this is where the problem is
            }
         }
     }

Answer 2

words[i] 可以为空。

您可以在抛出的行上放置一个断点，然后在“观察”窗口中检查words[i] 的值。