using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var xxx = new XXX();

        Console.WriteLine(xxx.ToString());

        ref int refVar = ref xxx.getValue(3);

        refVar = 12;

        Console.WriteLine(xxx.ToString());

    }

}

​

​

public class XXX {

    private int[] _a = new int[] {1,2,3,4,5,6};

    public ref int getValue(int idx) { return ref _a[idx]; }

    public override string ToString() { return string.Join(", ", _a.Select(x=>x.ToString()).ToArray()); }

}