如何在List< string>中使用Exist在C#中 [英] how to use Exist in List<string> in C#

问题描述

我必须查找列表中是否存在字符串，以避免重复插入:这是Microsoft网站上的示例:

I have to find if string exist in a list to avoid duplicates inserts: Here is example from Microsoft site:

using System;
using System.Collections.Generic;

public class Example
{
    public static void Main()
    {
        List<string> dinosaurs = new List<string>();

        dinosaurs.Add("Compsognathus");
        dinosaurs.Add("Amargasaurus");
        dinosaurs.Add("Oviraptor");
        dinosaurs.Add("Velociraptor");
        dinosaurs.Add("Deinonychus");
        dinosaurs.Add("Dilophosaurus");
        dinosaurs.Add("Gallimimus");
        dinosaurs.Add("Triceratops");

        Console.WriteLine();
        foreach(string dinosaur in dinosaurs)
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine("\nTrueForAll(EndsWithSaurus): {0}",
            dinosaurs.TrueForAll(EndsWithSaurus));

        Console.WriteLine("\nFind(EndsWithSaurus): {0}", 
            dinosaurs.Find(EndsWithSaurus));

        Console.WriteLine("\nFindLast(EndsWithSaurus): {0}",
            dinosaurs.FindLast(EndsWithSaurus));

        Console.WriteLine("\nFindAll(EndsWithSaurus):");
        List<string> sublist = dinosaurs.FindAll(EndsWithSaurus);

        foreach(string dinosaur in sublist)
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine(
            "\n{0} elements removed by RemoveAll(EndsWithSaurus).", 
            dinosaurs.RemoveAll(EndsWithSaurus));

        Console.WriteLine("\nList now contains:");
        foreach(string dinosaur in dinosaurs)
        {
            Console.WriteLine(dinosaur);
        }

        Console.WriteLine("\nExists(EndsWithSaurus): {0}", 
            dinosaurs.Exists(EndsWithSaurus));
    }

    // Search predicate returns true if a string ends in "saurus".
    private static bool EndsWithSaurus(String s)
    {
        return s.ToLower().EndsWith("saurus");
    }
}

是否可以用lambda表达式替换 EndsWithSaurus 函数?谢谢大家的投入！！这是一个工作代码:

Is it possible to replace EndsWithSaurus function with lambda expression? Thanks everybody for your input!! Here is a working code:

        if (dinosaurs.Any(e => e.EndsWith("saurus")))
            Console.WriteLine("saurus exists");

        if (dinosaurs.Exists(e => e.EndsWith("saurus")))
            Console.WriteLine("saurus exists");

推荐答案

尝试一下:

if (dinosaurs.Exists(e => e.EndsWith("saurus")))
        Console.WriteLine("saurus exists");

Any()的答案也很好.区别只是 Exists()方法本身来自 List< T> 本身，而 Any()只是Linq扩展的重要功能之一方法(并且需要使用System.Linq )

The answer with Any() works fine too. The difference is just the Exists() method comes from List<T> itself and the Any() is just one of the great Linq extension methods (and will require using System.Linq)

这篇关于如何在List< string>中使用Exist在C#中的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！