using System;

using System.Globalization;

public class Program

{

    public static void Main(string[] args)

    {

        string[] array = new string[]{"a", "b", "c", "d"};

        string refFormat = "{2} {0}";

        string newStr = String.Format(refFormat,array);

        Console.Write(newStr);

    }

}

​

​