Random Time Generator for Time Between Time NOW to 23.99 (End of the Current Day)

Question

I created some code and classes to get a random Hour and Minute between current time (NOW) and the End of the Day. My code works, but some times the times are wrong.

Lets say it's 11:30 PM and I run the code, I get WRONG output, where the write output is shown below... The values Must be in order from NOW (when executed) to End of the Current Day.

Does anyone know what I'm doing wrong?

WRONG (hour/minute):

• 0:23 - 12:23 AM (next day)
• 23:15 - 11:15 PM

RIGHT (hour/minute):

• 23:15 - 11:15 PM
• 0:23 - 12:23 AM (next day)

public class MyHourMinuteTestClass
{
   ArrayList projects  = new ArrayList();
   TimeSpan start = DateTime.Now.TimeOfDay;
   TimeSpan s = TimeSpan.FromHours(DateTime.Now.Hour);
   TimeSpan e = TimeSpan.FromHours(23.99);
   int maxMin = (int)((e - s).TotalMinutes);

   public MyHourMinuteTestClass()
   {
   }

   public void TestValues()
   {
       // create 2 sets of values and add a new SocialTimes instance containing the hour/minute to the array list
      for(int i = 0; i < 2; i++)
      {
          int minutes = randomGen.Next(maxMin);
          TimeSpan t = start.Add(TimeSpan.FromMinutes(minutes));
          int PostTimeHour = t.Hours;
          int PostTimeMinutes = t.Minutes;
          projects.Add(new SocialTimes(NowDateStr, PostTimeHour, PostTimeMinutes));
      }

      // then I sort the projects array list
      projects.Sort(new hoursMinutesComparer());
    }
}

public class SocialTimes
{
        string DateToPostStr = "";
        public int HourToPost = 0;
        public int MinuteToPost = 0;

        public SocialTimes(string DateToPostStr, int HourToPost, int MinuteToPost)
        {
            this.DateToPostStr = DateToPostStr;
            this.HourToPost = HourToPost;
            this.MinuteToPost = MinuteToPost;
        }

        public string getDateToPostStr()
        {
            return this.DateToPostStr;
        }

        public int getHourToPost()
       {
            return this.HourToPost;
        }

        public int getMinuteToPost()
        {
            return this.MinuteToPost;
        }

        public int getHourMinuteToPost()
        {
            int sum;

            sum = HourToPost * 60 + MinuteToPost;

            return sum;
        }
 }

public class hoursMinutesComparer : IComparer
{
     int IComparer.Compare(Object xx, Object yy)
     {
         SocialTimes x = (SocialTimes)xx;
         SocialTimes y = (SocialTimes)yy;

         return x.getHourMinuteToPost().CompareTo(y.getHourMinuteToPost());
      }
 }

Answer 1

That's some wordy code. Let's see if I can reduce it a bit/give a code block you can use for inspiration (because this seems like a homework)

public class Project{
  public Guid ID { get; set;}
  public DateTime Created{ get; set; }
}

public static class ProjectFactory{
  private static Random _r = new Random();

  public static Project CreateProject(){

    DateTime midnightTomorrow = DateTime.Today.AddDays(1);
    int secTilDayEnd = (int)(midnightTomorrow - DateTime.Now).TotalSeconds; 

    return new Project(){
      ID = Guid.NewGuid(),
      Created = DateTime.Now.AddSeconds(_r.Next(secTilDayEnd))
    };
  }
}

//and to use it

List<Project> p = new List<Project>(1000);
for(int i = 0; i < 1000; i++)
  p.Add(ProjectFactory.CreateProject());

foreach(var x in p.OrderBy(proj => proj.Created))
  Console.WriteLine($"Project {x.Id} created {x.Created:HH:mm}");

Let's store the random time in a datetime; we can always dig the time bit out if we want only that but keeping the date is helpful to retain. It also means we can just use default date time comparisons built into c# - it knows how to order dates

I created a class that has a sole job to manufacture projects with a created date of some time between now and the end of the day. It does this by working out how many seconds til the end of the day and adding a random number of those seconds to the current time

And then a code fragment to create a thousand projects, order them by the date and print them out, showing the time only

Answer 2

I think part of your problem is this...

TimeSpan s = TimeSpan.FromHours(DateTime.Now.Hour);

That is basically rounding down the current time to the nearest hour. If it's currently 11:30 PM, then...

// This is pseudocode
s = 23h
e = 24h
maxMin = e - s = 1h

So, you are allowing randomGen.Next(maxMin) to generate a number of minutes up to a full hour even though it's less than an hour to midnight. To fix this, I think you just need to get the total time represented in hours...

TimeSpan s = TimeSpan.FromHours(DateTime.Now.TimeOfDay.TotalHours);

Then you'd have...

// This is pseudocode
s = 23h30m
e = 24h
maxMin = e - s = 30m

Therefore, randomGen.Next(maxMin) could result in at most, (just under) 30 minutes, taking you to midnight.

A few other notes:

• I think using 23.99 makes it impossible to ever calculate 11:59 PM.

  TimeSpan s = TimeSpan.FromHours(DateTime.Now.TimeOfDay.TotalHours); //  23h30m
  TimeSpan e = TimeSpan.FromHours(23.99);                             // <24h
  //                 (e - s).TotalMinutes                             //    <30m
  int maxMin = (int)((e - s).TotalMinutes);                           //     29m
  int minutes = randomGen.Next(maxMin);                               //     28m (Max)
  TimeSpan t = start.Add(TimeSpan.FromMinutes(minutes));              //  23h58m
  

  e - s is just under 30 minutes to midnight. (int) truncates that to an even 29 minutes. The parameter to Random.Next() is the exclusive upper bound, so passing 29 means the highest value it can return is only 28.
• It seems like it would simplify things for SocialTimes to just store its data as a TimeSpan or even DateTime and then expose Hour and Minute properties, if desired.
• Be sure to look into the List<> generic class, which long ago superseded ArrayList.