C#:Dictionary的[string]索引器返回什么？

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        Dictionary<string, int> dictionary = new Dictionary<string, int>();
        dictionary.Add("apple", 5);
        dictionary.Add("banana", 3);

        int appleCount = dictionary["apple"];
        int bananaCount = dictionary["banana"];

        Console.WriteLine($"Apple count: {appleCount}");
        Console.WriteLine($"Banana count: {bananaCount}");
    }
}

Apple count: 5
Banana count: 3