具有多个键的字典不能按预期工作

我正在制作一个控制台程序，其中我有多个值映射到dictionary keyLookup。我正在使用if命令，使用键输出一些console.writeline = ("stuff");，但只有当我的值和键相同(在字典中)时才有效。我不知道这是为什么。我一直在玩弄list和foreach和一些变量试图找出我做错了什么，但即使它继续工作，它现在如何工作，它仍然不工作我想要的方式。

同样，如果我的console.readline();中有一个词不在我的字典中，整个事情就会崩溃。这是我不想要的，我也不确定它为什么要这样做，因为在某种程度上它没有这样做。此外，我的mathFunction字典工作就像我想我的keyLookup字典工作。虽然我认为不同之处在于我如何使用列表来交叉引用keyLookup。

class MainClass
    {
        public static string Line;
        static string foundKey;
        public static void Main (string[] args)
        {
            while (true) 
            {
                if (Line == null)
                {Console.WriteLine ("Enter Input"); }
                WordChecker ();
            }
    }
    public static void WordChecker()
    {
        string inputString = Console.ReadLine ();
        inputString = inputString.ToLower();  
        string[] stripChars = { ";", ",", ".", "-", "_", "^", "(", ")", "[", "]",
            "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "'n", "'t", "'r" };
        foreach (string character in stripChars)
        {
            inputString = inputString.Replace(character, "");
        }
        // Split on spaces into a List of strings
        List<string> wordList = inputString.Split(' ').ToList();
        // Define and remove stopwords
        string[] stopwords = new string[] { "and", "the", "she", "for", "this", "you", "but" };
        foreach (string word in stopwords)
        {
            // While there's still an instance of a stopword in the wordList, remove it.
            // If we don't use a while loop on this each call to Remove simply removes a single
            // instance of the stopword from our wordList, and we can't call Replace on the
            // entire string (as opposed to the individual words in the string) as it's
            // too indiscriminate (i.e. removing 'and' will turn words like 'bandage' into 'bdage'!)
            while ( wordList.Contains(word) )
            {
                wordList.Remove(word);
            }
        }
        // Create a new Dictionary object
        Dictionary<string, int> dictionary = new Dictionary<string, int>();
        // Loop over all over the words in our wordList...
        foreach (string word in wordList)
        {
            // If the length of the word is at least three letters...
            if (word.Length >= 3) 
            {
                // ...check if the dictionary already has the word.
                if ( dictionary.ContainsKey(word) )
                {
                    // If we already have the word in the dictionary, increment the count of how many times it appears
                    dictionary[word]++;
                }
                else
                {
                    // Otherwise, if it's a new word then add it to the dictionary with an initial count of 1
                    dictionary[word] = 1;
                }
            }
            List<string> dicList = new List<string>();
            dicList = dictionary.Keys.ToList ();
            Dictionary<string, string> keyLookup = new Dictionary<string, string>();
            keyLookup["hey"] = "greeting";
            keyLookup["hi"] = "greeting";
            keyLookup["greeting"] = "greeting";
            keyLookup["math"] = "math";
            keyLookup["calculate"] = "math";
            keyLookup["equation"] = "math";
            foundKey = keyLookup[word];
            List<string> keyList = new List<string>();
            foreach (string keyWord in dicList)
            {
                if(keyWord == foundKey)
                {keyList.Add (keyWord); }
            }
            foreach (string mKey in keyList)
            {
            if(mKey == "greeting")
            {Greetings ();}
            if (mKey == "math") 
            {Math ();}
            }
        }
    }
    public static void Math()
    {
        Console.WriteLine ("What do you want me to math?");
        Console.WriteLine ("input a number");
        string input = Console.ReadLine ();
        decimal a = Convert.ToDecimal (input);
        Console.WriteLine("Tell me math function");
        string mFunction = Console.ReadLine();
        Console.WriteLine ("tell me another number");
        string inputB = Console.ReadLine();
        decimal b = Convert.ToDecimal (inputB);
        Dictionary<string, string> mathFunction = new Dictionary<string, string>();
        mathFunction["multiply"] = "multiply";
        mathFunction["times"] = "multiply";
        mathFunction["x"] = "multiply";
        mathFunction["*"] = "multiply";
        mathFunction["divide"] = "divide";
        mathFunction["/"] = "divide";
        mathFunction["subtract"] = "subtract";
        mathFunction["minus"] = "subtract";
        mathFunction["-"] = "subtract";
        mathFunction["add"] = "add";
        mathFunction["+"] = "add";
        mathFunction["plus"] = "add";
        string foundKey = mathFunction[mFunction];
        if (foundKey == "add")
        {
            Console.WriteLine (a + b);
        }
        else if (foundKey == "subtract")
        {
            Console.WriteLine (a - b);
        }
        else if (foundKey == "multiply")
        {
            Console.WriteLine (a * b);
        }
        else if (foundKey == "divide")
        {
            Console.WriteLine (a / b);
        }
        else
        {
            Console.WriteLine ("not a math");
        }
    }
    public static void Greetings()
    {
        Console.WriteLine("You said hello");
    }
}'