如何使用C#中的List <string>中的Exist

Question

我必须找到列表中是否存在字符串以避免重复插入:以下是来自Microsoft站点的示例:

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EndsWithSaurus用lambda表达式替换函数？谢谢大家的意见!这是一个有效的代码:

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

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

Answer 1

试试这个:

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

答案也Any()很好.区别在于Exists()方法来自于List<T>自身,而且Any()只是Linq扩展方法之一(并且需要using System.Linq)

Answer 2

用途Any:

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

你可以List.Exists()通过改变你的lambda 来使用:

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

但是Any更便携(即可以与任何可枚举的,而不仅仅是Lists一起使用).