C#中索引器探索

class MyDictionary
{
    private string[] keys;
    private string[] values;

    public MyDictionary()
    {
        keys = new string[10];
        values = new string[10];
    }

    public string this[string key]
    {
        get
        {
            int index = Array.IndexOf(keys, key);
            if (index >= 0)
            {
                return values[index];
            }
            else
            {
                return null;
            }
        }

        set
        {
            int index = Array.IndexOf(keys, key);
            if (index >= 0)
            {
                values[index] = value;
            }
            else
            {
                int emptyIndex = Array.IndexOf(keys, null);
                if (emptyIndex >= 0)
                {
                    keys[emptyIndex] = key;
                    values[emptyIndex] = value;
                }
                else
                {
                    throw new Exception("Dictionary is full.");
                }
            }
        }
    }
}

class Program
{
    static void Main(string[] args)
    {
        MyDictionary dictionary = new MyDictionary();
        dictionary["Apple"] = "A fruit";
        dictionary["Orange"] = "Another fruit";
        
        Console.WriteLine(dictionary["Apple"]);   // 输出：A fruit
        Console.WriteLine(dictionary["Orange"]);  // 输出：Another fruit
        
        Console.ReadKey();
    }
}