using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var DateList = new List<DateTime>{DateTime.Now, DateTime.Today, DateTime.Now.AddDays(-2)}; // your populated list of dates

        var allDaysOfWeek = Enum.GetValues(typeof (DayOfWeek)).Cast<DayOfWeek>();

        var totalDayCounts = allDaysOfWeek.GroupJoin(DateList, dayOfWeek => dayOfWeek, date => date.DayOfWeek, (dayOfWeek, times) => new {DayOfTheWeek = dayOfWeek, DayOfWeekCount = times.Count()}     );

        foreach (var i in totalDayCounts)

        {

            Console.WriteLine(i);

        }

    }

}