using System;

using System.Globalization;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main() {

        var userActions = new [] { 

            new UserAction { UserName = "Lisa", Action = CrudAction.Edited, Date = DateTime.ParseExact("2018-05-20 09:46", "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture)},

            new UserAction { UserName = "Tom",  Action = CrudAction.Edited, Date = DateTime.ParseExact("2018-05-18 11:18", "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture)},

            new UserAction { UserName = "Tom",  Action = CrudAction.Edited, Date = DateTime.ParseExact("2018-05-18 11:18", "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture)},

            new UserAction { UserName = "Tom",  Action = CrudAction.Edited, Date = DateTime.ParseExact("2018-05-18 11:18", "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture)},

            new UserAction { UserName = "Tom",  Action = CrudAction.Edited, Date = DateTime.ParseExact("2018-05-18 11:16", "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture)},

            new UserAction { UserName = "Tom",  Action = CrudAction.Edited, Date = DateTime.ParseExact("2018-05-18 11:15", "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture)},

            new UserAction { UserName = "Tom",  Action = CrudAction.Edited, Date = DateTime.ParseExact("2018-05-18 11:15", "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture)},

            new UserAction { UserName = "Tom",  Action = CrudAction.Edited, Date = DateTime.ParseExact("2018-05-18 11:15", "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture)},

            new UserAction { UserName = "Tom",  Action = CrudAction.Edited, Date = DateTime.ParseExact("2018-05-18 10:12", "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture)},

            new UserAction { UserName = "Lisa", Action = CrudAction.Edited, Date = DateTime.ParseExact("2018-05-16 13:28", "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture)},

            new UserAction { UserName = "Lisa", Action = CrudAction.Posted, Date = DateTime.ParseExact("2018-05-16 13:25", "yyyy-MM-dd HH:mm", CultureInfo.InvariantCulture)},

        };

        var distinctActions = userActions

            .OrderByDescending(ua => ua.Date)

            .Distinct(new UserNameActionAndHourComparer());

        foreach (var unique in distinctActions) {

            Console.WriteLine(unique.UserName  + "\t" + unique.Action.ToString("G") + "\t" + unique.Date.ToLongDateString() + " " + unique.Date.ToLongTimeString());

        }

    }

    public class UserNameActionAndHourComparer : IEqualityComparer<UserAction> {

        public bool Equals(UserAction left, UserAction right){

            if (left == null && right == null) {

                 return true;

            }

            if (left == null | right == null) {

                return false;

            }

​

            if(left.UserName == right.UserName && left.Action == right.Action) {

                return left.Date.Date == right.Date.Date && left.Date.Hour == right.Date.Hour;

            }

​

            return false;

       }

        public int GetHashCode(UserAction ua) {

            return ua.UserName.GetHashCode() 

                ^ ua.Action.GetHashCode() 

                ^ new DateTime(ua.Date.Year, ua.Date.Month, ua.Date.Day, ua.Date.Hour, 0, 0).GetHashCode();

        }

    }

    public class UserAction {

        public int LogId { get; set; }

        public string UserName { get; set; }

        public CrudAction Action { get; set; }

        public DateTime Date{ get; set; }

    }

    public enum CrudAction {

        Posted,

        Edited       

    }

}