// C# Extension Method

// Doc: https://csharp-extension.com/en/method/1002632/array-asreadonly

​

// @nuget: Z.ExtensionMethods

​

using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        String[] myArr = { "The", "quick", "brown", "fox" };

​

        Console.WriteLine("The string array initially contains the following values:");

        PrintIndexAndValues(myArr);

​

        // Create a read-only IList wrapper around the array.

        // C# Extension Method: Array - AsReadOnly

        IList<String> myList = myArr.AsReadOnly();

​

        Console.WriteLine("The read-only IList contains the following values:");

        PrintIndexAndValues(myList);

​

        try

        {

            myList[3] = "CAT";

        }

        catch (NotSupportedException e)

        {

            Console.WriteLine("{0} - {1}", e.GetType(), e.Message);

            Console.WriteLine();

        }

​

        myArr[2] = "RED";

​

        Console.WriteLine("After changing the third element, the string array contains the following values:");

        PrintIndexAndValues(myArr);

​

        Console.WriteLine("After changing the third element, the read-only IList contains the following values:");

        PrintIndexAndValues(myList);

​

    }

​

    public static void PrintIndexAndValues(String[] myArr)

    {

        for (int i = 0; i < myArr.Length; i++)

        {

            Console.WriteLine("   [{0}] : {1}", i, myArr[i]);

        }

        Console.WriteLine();

    }

​

    public static void PrintIndexAndValues(IList<String> myList)

    {

        for (int i = 0; i < myList.Count; i++)

        {

            Console.WriteLine("   [{0}] : {1}", i, myList[i]);

        }

        Console.WriteLine();

    }

}