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Dynamic Calendar Web Application in ASP.NET 2.0


Very often, you will find calendars on various website, where a date can be labeled as a holiday, a special event, a birthday etc... However, it would be really cumbersome to update the HTML page each time there is an event on a specific date.


This is where the power of ASP.NET comes into picture. Linking a database of events and the dates to our page, we can dynamically generate a calendar which will show the required information on specific dates.


In this tutorial, we will consider a list of events that will be stored in database to be retrieved and properly label a date if an event falls on that date.

Below is a list of sample data that will be used in the tutorial.

Event Date
New Year 1st Jan to 2nd of Jan 2007
Independence Day 5th Feb 2007
Dad's Birthday 3rd March 2007
Valentine's Day! 4th April 2007
Wife's Birthday 30th May 2007
Camping with friends 5th June to 10th June 2007
Mum's Birthday 8th July 2007
Christmas 25th Dec 2007
Brother's Birthday 26th Dec 2007

Fig 1. List of sample events for the application

Database Design for Calendar web application

An MS Access database named "Events" is created to hold the events. There will be only 1 table named "Events" that will hold the information. The fieldnames are self-explanatory, as shown in the figure 2. For simplicity, we will manually fill in the data and make sure that Date From will not be greater than Date To.

Table definition for Calendar web application
Fig 2. Table definition for holding the events

Data used in Calendar application
Fig 3. Populated table containing list of events. Date format (mm/dd/yyyy)

Screen and CSS Design

We will only have one page holding the calendar for year 2007. The page will only contain a title and a label. It is the label that will hold the generated calendar as will be shown later.

A nice CSS will also be linked with the page. Of course you are free to modify the CSS as per your taste. The important CSS classes that will be used are:

  • calendarFrame

  • calendarMonthYear

  • calendarDay

  • hasEvent

  • hasNoEvent

The calendar style that will be displayed will look like as in figure 5.

Calendar control style
Fig 5. Sample calendar showing the month March 2007.

Coding the Calendar Generator

A year consists of 12 months. The months will be layout in a table of 4 rows x 3 columns.

Each month will consist of a maximum of 6 rows x 7 columns. The columns will represent the days, starting with Sunday to Saturday. A maximum of 6 rows can be obtained when the 1st of a 31-day month falls on a Saturday.

To generate calendar for the year 2207, the following code is used:

If Not IsPostBack Then
'  Generates report for current year
      lblCalendar.Text = "<table width='600px'>"
'   number of months in horizontal direction
      Dim horizontalRepeat As Integer = 3    
Dim month As Integer
      For month = 1 To 12
            If (month Mod horizontalRepeat = 1) Then
                  lblCalendar.Text += "<tr valign='top'>"
End If
            lblCalendar.Text += "<td>" + generateCalendar(month, 2007) + "</td>"
If (month Mod horizontalRepeat = 0) Then
                  lblCalendar.Text += "</tr>"
End If
lblCalendar.Text += "</table>"
End If

The calendar is being dynamically constructed, starting with the big table 4 rows x 3 columns. We skip to the next row when "month Mod horizontalRepeat = 1", that is, when month value is 1, 4, 7 and 10. We should not forget to close every HTML tag!

The method generateCalendar (month, 2007) returns a string containing an HTML table that represents a specific month and put in between <td></td> tags.

The method below shows how a month is filled with dates and on which day the dates fall.

'  generates the calendar as per the booking status
Dim wholeCalendar(5, 6) As Integer
Dim weeks As Integer = 0
Dim day As String = ""
Dim tmpDate As DateTime
Dim myDate As Integer
For myDate = 1 To 31
        tmpDate = New DateTime(year, month, myDate)
        If (day = "Saturday") Then
            weeks += 1
        End If
        day = tmpDate.DayOfWeek.ToString()
        If (day = "Sunday") Then
            wholeCalendar(weeks, 0) = myDate
        ElseIf (day = "Monday") Then
            wholeCalendar(weeks, 1) = myDate
        ElseIf (day = "Tuesday") Then
            wholeCalendar(weeks, 2) = myDate
        ElseIf (day = "Wednesday") Then
            wholeCalendar(weeks, 3) = myDate
        ElseIf (day = "Thursday") Then
            wholeCalendar(weeks, 4) = myDate
        ElseIf (day = "Friday") Then
            wholeCalendar(weeks, 5) = myDate
        ElseIf (day = "Saturday") Then
            wholeCalendar(weeks, 6) = myDate
        End If
    Catch ex As Exception
        Exit For
    End Try

The code snippet shows the beauty of the try ... catch block. It completely eliminates the test whether February has to contain 28 or 29 days or whether a month should contain 30 or 31 days. First, an array 6 x 7 of integer (0...5, 0...6) is created to hold the date 1 to 31.

We start with the first row of the array, which in other terms represent the first week (week initially set to 0). Having the year, month and date, an object of DateTime is created. If there is an error, for example, 30th February, we know that the last day of the month has been passed (Refer to figure 5).

If the current day is Saturday, the next day will be on the next row, i.e. Sunday (start of the next week).

We get the day name from the method tmpDate.DayOfWeek.toString() which will return a value from Monday to Sunday. We then set the date in the corresponding cell. Sunday is in column 0; Monday is in column 1 and so on.

After filling the array with numbers, HTML code has to be generated for the current month. The following code snippet does the job.

'   Generates the HTML calendar
Dim htmlCalendar As String = ""
Dim objEventsDAO As New EventsDAO()
Dim dt As DataTable
Dim i As Integer, j As Integer
htmlCalendar += "<table class='calendarFrame' cellspacing=0>"
htmlCalendar += "<tr class='calendarMonthYear' style='text-align: center;'><td colspan='7'>" + getMonthName(month) + " " + year.ToString() + "</td></tr>"
htmlCalendar += "<tr class='calendarDay' style='text-align: center;'> <td>Sun</td>  <td>Mon</td>  <td>Tue</td>  <td>Wed</td>  <td>Thu</td>  <td>Fri</td>  <td>Sat</td> </tr>"
For i = 0 To 5
htmlCalendar += "<tr>"
For j = 0 To 6
        If wholeCalendar(i, j) > 0 Then
           dt = objEventsDAO.GetEvent(wholeCalendar(i, j), month, year)
           If (dt.Rows.Count > 0) Then
           Dim toolTip As String = dt.Rows(0)("Event").ToString()
           htmlCalendar += "<td class='hasEvent' title=""" + toolTip + """>" + wholeCalendar(i, j).ToString() + "</td>"
           htmlCalendar += "<td class='hasNoEvent'>" + wholeCalendar(i, j).ToString() + "</td>"
           End If
htmlCalendar += "<td class='hasNoEvent'>&nbsp;</td>"
  End If
htmlCalendar += "</tr>"
htmlCalendar += "</table>"
'   Close database connection

A class called EventsDAO is created containing methods to check whether on a particular date there is an event or not. Please refer to the attached code for getting the code. The SQL commands are simple and self explanatory.

The string htmlCalendar holds the HTML code for the month table, with the proper CSS class and table title for the current month and year.

Then using the array that was previously filled:

  • If current array cell contains a zero value, a space; &nbsp; is placed in between <td></td> tags having the CSS class hasNoEvent.

  • If current array cell value is associated with an event, wholeCalendar(i, j).ToString() is placed in between <td></td> tags with the CSS class hasEvent. Also, when the mouse pointer is moved on the date, a tooltip is shown containing the event description by adding the attribute Title to the <td> element.

  • If current array cell value is not associated with an event, the value wholeCalendar(i,j).ToString() is placed in between <td></td> tags with the CSS class hasNoEvent.

Here is a sample look at the output fro the first 6 months, as seen in a browser.

Sample output of calendar for year 2007
Fig 6. Sample output of calendar for year 2007

There we are! You can try the sample Calendar web application, attached for seeing the result.

Improvements / Enhancements

The tutorial is a kick start to get your creativity going. A few suggestions to improve the calendar:

  • Try accommodating different CSS class to different kind of events. For example, public holidays can have red background circle. Note that you should change the MS Access table as well.

  • Try changing the "year" parameter when generating the calendar to see different results. E.g. generateCalendar(month, 2010) or generateCalendar(month, 2006)

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