如何在 C# 中的 List<string> 中使用 Exist
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how to use Exist in List<string> in C#
提问by GenZiy
I have to find if string exist in a list to avoid duplicates inserts: Here is example from Microsoft site:
我必须查找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");
}
}
Is it possible to replace EndsWithSaurusfunction with lambda expression?
Thanks everybody for your input!! Here is a working code:
是否可以EndsWithSaurus用 lambda 表达式替换函数？感谢大家的投入！！这是一个工作代码：
if (dinosaurs.Any(e => e.EndsWith("saurus")))
Console.WriteLine("saurus exists");
if (dinosaurs.Exists(e => e.EndsWith("saurus")))
Console.WriteLine("saurus exists");
采纳答案by Sevenate
Try this:
尝试这个：
if (dinosaurs.Exists(e => e.EndsWith("saurus")))
Console.WriteLine("saurus exists");
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)
的答案也Any()很好用。不同之处在于Exists()方法来自于List<T>它本身，Any()它只是一个伟大的 Linq 扩展方法（并且需要using System.Linq）
回答by D Stanley
Use Any:
使用Any：
if (dinosaurs.Any(e => e.EndsWith("saurus")))
Console.WriteLine("saurus exists");
You coulduse List.Exists()by just changing your lambda:
您只需更改 lambda即可使用List.Exists()：
if (dinosaurs.Exists(e => e.EndsWith("saurus")) // == true is implied
Console.WriteLine("saurus exists");
but Anyis more portable (i.e. can be used with anyenumerable, not just Lists.
但Any更便携（即可以与任何可枚举一起使用，而不仅仅是Lists.
