How to mimic the Outlook group name style ?

Recently, I had to sort items in my listview. Ok, I heard you, “nothing difficult doing that”. But I also had to group them as Outlook does. I mean “according to the date, today items, yesterday items, tomorrow items, next month items,…”

First of all we have to define the label for each group:

private void Form1_Load(object sender, EventArgs e)
{
  string[] groupName = {&quot;Older&quot;,
      &quot;Last month&quot;, &quot;4 weeks ago&quot;, &quot;3 weeks ago&quot;, &quot;2 weeks ago&quot;, &quot;Last week&quot;,
      &quot;Monday&quot;, &quot;Tuesday&quot;, &quot;Wednesday&quot;, &quot;Thursday&quot;, &quot;Friday&quot;, &quot;Saturday&quot;, &quot;Sunday&quot;,
      &quot;Yesterday&quot;,
      &quot;Today&quot;,
      &quot;Tomorrow&quot;,
      &quot;Monday&quot;, &quot;Tuesday&quot;, &quot;Wednesday&quot;, &quot;Thursday&quot;, &quot;Friday&quot;, &quot;Saturday&quot;, &quot;Sunday&quot;,
      &quot;Next week&quot;, &quot;In 2 weeks&quot;, &quot;In 3 weeks&quot;, &quot;In 4 weeks&quot;, &quot;Next month&quot;,
      &quot;Newer&quot;};

  // populate the group list
  foreach(string group in groupName)
    listView1.Groups.Add(new ListViewGroup(group));
}

Then we have to define what group an item belongs to according to the current date and the item’s date.

internal static int GetDateTimeGroupIndex(DateTime dtRef, DateTime dtSource)
{
  // Because week starts on Monday in France
  int dtWeekDay = (Convert.ToInt32(dtSource.DayOfWeek) + 6) % 7;
  int dtRefWeekDay = (Convert.ToInt32(dtRef.DayOfWeek) + 6) % 7;

  int ts = (dtRef.Date - dtSource.Date).Days;

  if (ts == 0)
    return 0; // same day
  if (ts == 1)
    return -1; // day before

  if (ts == -1)
    return 1; // day after

  // same week
  if ((ts &gt; 1) &amp;&amp; (ts &lt;= dtRefWeekDay)) 
    return dtWeekDay - 8;
  if ((-ts &gt; 1) &amp;amp;&amp;amp; (-ts &lt;= 6 - dtRefWeekDay))
    return dtWeekDay + 2;

  // previous / next weeks
  for (int nIdx = 0; nIdx &lt;= 3; nIdx++) 
  {
    if ((ts &gt; dtRefWeekDay + nIdx * 7) &amp;&amp; (ts &lt;= dtRefWeekDay + (nIdx + 1) * 7)) 
      if (dtRef.Month == dtSource.Month) 
        return -(9 + nIdx); 
      else 
        return -13; 
    if ((-ts &gt; 6 - dtRefWeekDay + nIdx * 7) &amp;&amp; (-ts &lt;= 6 - dtRefWeekDay + (nIdx + 1) * 7))
      if (dtRef.Month == dtSource.Month)
        return (9 + nIdx);
      else
        return 13;
  }

  if (Math.Abs(dtSource.Month - dtRef.Month) == 1)
    return Math.Sign(ts) * (-13);

  return Math.Sign(ts) * (-14);
}

Finally we have to set for every item the Group property as follow:

DateTime dtDate = DateTime.Now.AddMonths(-2);
while(dtDate &lt; DateTime.Now.AddMonths(2))
{
  ListViewItem item = new ListViewItem(&quot;Item &quot; + dtDate.Date.ToString(&quot;dd/MM/yyyy&quot;));
  item.Group = listView1.Groups[GetDateTimeGroupIndex(DateTime.Now, dtDate) + 14];
  listView1.Items.Add(item);
  dtDate = dtDate.AddDays(1);
}

And the result is …

PS: as I am French, weeks start on monday, sorry 😉

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