Overloaded Indexers ใน C# (Indexer หลายรูปแบบ)

Indexer ทำให้ Object เข้าถึงได้แบบ Array (用 [ ]) Indexers สามารถ Overload ได้ และรับ Parameters หลายตัว ชนิดต่างกันได้

ตัวอย่าง Overloaded Indexers

using System;

namespace IndexerApplication
{
    class IndexedNames
    {
        private string[] namelist = new string[size];
        static public int size = 10;

        public IndexedNames()
        {
            for (int i = 0; i < size; i++) namelist[i] = "N. A.";
        }

        // Indexer 1: int parameter
        public string this[int index]
        {
            get
            {
                string tmp = "";
                if (index >= 0 && index <= size - 1) tmp = namelist[index];
                return tmp;
            }
            set
            {
                if (index >= 0 && index <= size - 1) namelist[index] = value;
            }
        }

        // Indexer 2: string parameter
        public int this[string name]
        {
            get
            {
                int index = 0;
                while (index < size)
                {
                    if (namelist[index] == name) return index;
                    index++;
                }
                return index;
            }
        }

        static void Main(string[] args)
        {
            IndexedNames names = new IndexedNames();
            names[0] = "John"; names[1] = "Joe"; names[2] = "Graham";
            names[3] = "William"; names[4] = "Jack"; names[5] = "Tom"; names[6] = "Tim";

            // ใช้ Indexer int
            for (int i = 0; i < IndexedNames.size; i++) Console.WriteLine(names[i]);

            // ใช้ Indexer string
            Console.WriteLine(names["Nuha"]); // 10 (Not found = size)
            Console.ReadKey();
        }
    }
}

Output

John Joe Graham William Jack Tom Tim N. A. N. A. N. A. 10