using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var list = new List<MyClass>()

        {new MyClass{Id = 1, Value = 3}, new MyClass{Id = 2, Value = 4}, };

        var result = list.SelectMany(x => Enumerable.Repeat(x.Id, x.Value)).ToArray();

        foreach (var element in result)

        {

            Console.WriteLine(element);

        }

    }

}

​

class MyClass

{

    public int Id

    {

        get;

        set;

    }

​

    public int Value

    {

        get;

        set;

    }

}