using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public void Main()

    {

        int numberOfItems = 15;

        List<string> collection = new List<string>();

        for (var i = 0; i < numberOfItems; i++)

            collection.Add((i + 1).ToString());

        int numberOfColumns = 2;

        for (var c = 0; c < numberOfColumns; c++)       

            Console.WriteLine("Items: " + numberOfItems+ ", Columns: " + numberOfColumns + ", Column: " + (c + 1)  + ", Items in column: " + CalculateColumnItems(collection, numberOfColumns, c + 1));

    }

    private string CalculateColumnItems(List<string> collection, int numberOfColumns, int column)

    {

        int itemsPerColumn = (int)Math.Ceiling((double)collection.Count / numberOfColumns);

        var result = collection.Cast<object>().Skip(itemsPerColumn * (column - 1)).Take(itemsPerColumn);

        return string.Join(",", result);

    }

}