using System;

using System.Collections.Generic;

using System.Linq;

using System.Globalization;

​

public class Program

{

    public static void Main()

    {

        var list = new List<string>

        {

            "5:00", "6:00", "7:00", "8:00", "9:00", "10:00",

            "05:30", "6:30", "07:30", "8:30", "9:30"

        };

        var result = list.OrderBy(x => DateTime.ParseExact(x, "H:mm", CultureInfo.InvariantCulture));

        foreach (var item in result)

        {

            Console.WriteLine(item);

        }

    }

}