Customizing the Calendar control in ASP.NET

Recently I had to work on customizing an ASP.NET Calendar control by adding text to the day cells for my team's AppWeek project. This proved to be not as straight-forward as I thought so here is what I did in case someone else might want to do the same.

The best place to modify the text in a cell seems to be the DayRender event handler. So the first thing I tried was to just modify the e.Cell.Text property like this:

void Calendar1_DayRender(object sender, DayRenderEventArgs e)
    {
   
                    e.Cell.Text += “My text”;

}

The main problem was that after adding text to a day cell in the control I wasn't able to select that day by clicking on the day number. Here is what you can do if you still want the select day functionality:

void Calendar1_DayRender(object sender, DayRenderEventArgs e)
    {
                   AddTextToDayCell(e, Datetime.Today, “MyText“);

 

}

void AddTextToDayCell(DayRenderEventArgs e, Datetime d, string text)

{

         if(e.Day.Date == d.Date)

        {

                 string ID = ((System.TimeSpan)(e.Day.Date - new DateTime(2000, 1, 1))).Days.ToString();

                 e.Cell.Text = "<a href=\"javascript:__doPostBack('Calendar1','" + ID + "')\" style=\"color:#663399\">" + e.Day.DayNumberText; //assuming the name of the calendar control is Calendar1.

                 e.Cell.Text +=text;

          }

}

If you want your new text to act as a link to some other URL, you could modify the AddTextToCell function as follows:

  private void Calendar1_DayRender(object sender, System.Web.UI.WebControls.DayRenderEventArgs e)
  {
   AddTextToDayCell(e, DateTime.Today, "MyText", "https://www.msn.com"); //this will add the MyText link to https://www.msn.com to the current day's cell
  }
  
  void AddTextToDayCell(DayRenderEventArgs e, DateTime d, string text, string URL)

  {

   if(e.Day.Date == d.Date)

   {

    string ID = ((System.TimeSpan)(e.Day.Date - new DateTime(2000, 1, 1))).Days.ToString();

    e.Cell.Text = "<a href=\"javascript:__doPostBack('Calendar1','" + ID + "')\" style=\"color:#663399\">" + e.Day.DayNumberText;

    e.Cell.Text += "<br> <a href=\""+ URL + "\">" + text;

   }

  }

Hope you'll find this helpful. Btw, Microsoft is not liable in any way in case you have any trouble after using this code :)