如何获取列表中具有相同前缀的所有单词？ C#

Question

I am working on a college project and I am stumped on how to get all the words with the prefix ("he") printed using Console.WriteLine. Here is my code so far, as you can see I already tried but it is highlighting my GetWordsForPrefix("he") in red. Thank you, (dont mind the other stuff, it is other scenarios I have to implement)

` static void Main(string[] args) { List words = new List();

        words.Add("car");
        words.Add("caramael");
        words.Add("hey");
        words.Add("hello");
        words.Add("helloeverybody");
        words.Add("CSC204");


        // Console.WriteLine("Scenario 1:");
        // Console.WriteLine();
        // foreach (string word in words)
        // {
        //      Console.WriteLine(word);
        //  }

        foreach (string word in words.GetWordsForPrefix("he"))
        {
            Console.WriteLine(word);
        }

        Console.WriteLine("\nScenario 5 Printing all words:");
        words.Sort();

        Console.WriteLine();
        foreach (string word in words)
        {
            Console.WriteLine(word);
        }

        Console.WriteLine("\n Scenario 6 Insert  \"car\":");
        int index = words.BinarySearch("car");
        if (index < 0)
        {
            words.Insert(~index, "car");
        }
        

        Console.WriteLine();
        foreach (string word in words)
        {
            Console.WriteLine("Error, This word already exsits");
        }

    }


}` 

Answer 1

If words is a List, then use LINQ Where().

Make List of Words

List<string> words = new List<string>();
words.Add("car");
words.Add("caramael");
words.Add("hey");
words.Add("hello");
words.Add("helloeverybody");
words.Add("CSC204");

Query list of words

var results = words.Where( (x) => x.StartsWith("he"));

Answer 2

It is unclear if you are required to implement a method called GetWordsForPrefix . This method is obviously not a method in a List 's properties.

Also, as I commented, I am confident you would get an error on the line…

List words = new List();

A List needs a “type” of something. In this case I will assume you need a string type…

List<string> words = new List<string>();

Then to get all the words in the list that start with “he” could go something like…

foreach (string word in words) {
  if (word.StartsWith("he")) {
    Console.WriteLine(word);
  }
}

If you are required to implement a GetWordsForPrefix method, then that method would need a list of all words and a string “prefix.” Then the method would return a list of all the words that start with the given prefix. Something like…

private static List<string> GetWordsForPrefix(List<string> allWords, string prefix) {
  List<string> prefixWords = new List<string>();
  foreach (string word in allWords) {
    if (word.StartsWith(prefix)) {
      prefixWords.Add(word);
    }
  }
  return prefixWords;
}

Then you could call this method in a similar way as your current code. Something like…

foreach (string word in GetWordsForPrefix(words, "he")) {
  Console.WriteLine(word);
}