C# 字典通过索引获取项目

使用C#中的字典可以通过索引获取项目是一种非常方便和高效的方式。字典是一种键值对的集合，其中每个键都是唯一的，并与一个值相关联。通过使用键，我们可以快速地查找和访问与之相关联的值，而不需要遍历整个集合。

csharp
Dictionary dictionary = new Dictionary();

csharp
dictionary.Add("apple", 5);
dictionary.Add("banana", 3);
dictionary.Add("orange", 8);

csharp
int appleQuantity = dictionary["apple"];
Console.WriteLine(appleQuantity); // 输出：5

csharp
int quantity;
if (dictionary.TryGetValue("pear", out quantity))
{
    Console.WriteLine(quantity);
}
else
{
    Console.WriteLine("The key 'pear' does not exist in the dictionary.");
}

csharp
using System;
using System.Collections.Generic;
class Program
{
    static void Main(string[] args)
    {
        Dictionary studentAges = new Dictionary();
        studentAges.Add("John", 18);
        studentAges.Add("Alice", 20);
        studentAges.Add("Bob", 19);
        Console.WriteLine("Enter a student's name:");
        string name = Console.ReadLine();
        if (studentAges.ContainsKey(name))
        {
            int age = studentAges[name];
            Console.WriteLine("The age of {0} is {1}.", name, age);
        }
        else
        {
            Console.WriteLine("The student's name does not exist in the dictionary.");
        }
    }
}