Use index when querying array with LINQ : Index : LINQ C# Source Code

    
 
using System;
using System.Collections.Generic;
using System.Linq;
using System.Drawing;

public class Book {
    public String Title { get; set; }

    public override String ToString() {
        return Title;
    }
}

class Program {


    static public Book[] Books =
    {
      new Book {Title="F"},
      new Book {Title="B"}
    };

    static void Main(string[] args) {
        var books =
          Books
            .Select((book, index) => new { index, book.Title })
            .OrderBy(book => book.Title);
    }
}