Windows Control: The Month Calendar Control
Microsoft Windows provides a control used to select dates on a colorful calendar:
The dates used and the way they display are based on the Regional Settings of the Control Panel. It may also depend on the operating system. This convenient control is called month calendar or simply calendar. The title bar of the control displays two buttons and two labels. The left button allows the user to select the previous month by clicking the button. The left label displays the currently selected month. The right label displays the year of the displayed date. The right button is used to get to the next month.
The calendar can be configured to display more than one month. Here is an example that displays two months:
If the control is displaying more than one month, the buttons would increment or decrement by the previous or next month in the list. For example, if the control is displaying April and May and if the user clicks the left button, the control would display March and April. If the control is displaying April and May and the user clicks the right button, the control would display May and June. Also, to select any month of the current year, the user can click the name of the month, which displays the list of months and this allows the user to click the desired month:
To select a year, the user can click the year number. This changes the year label into a spin button:
To change the year, the user can click the up or down arrows of the spin button. As the spin button is displaying, the user can also use the arrow keys of the keyboard to increase or decrease the value.
Under the title bar, the short names of week days display, using the format set in Control Panel. In US English, the first day is usually Sunday. The first day can be changed by the programmer.
On the control, the currently selected date has a circle
around. To select a date on the control, the user clicks the desired date, which
changes from the previous selection.
To create a calendar control, you can click the MonthCalendar button in the Toolbox and click the form or the desired container. The MonthCalendar control is based on the MonthCalendar class, which is based on Control. Therefore, to create a calendar control, declare a variable or type MonthCalendar and initialize it appropriately. Here is an example:
Imports System.Drawing Imports System.Windows.Forms Module Exercise Public Class Starter Inherits Form Private Calendar As MonthCalendar Dim components As System.ComponentModel.Container Public Sub New() InitializeComponent() End Sub Public Sub InitializeComponent() Calendar = New MonthCalendar Controls.Add(Calendar) End Sub End Class Function Main() As Integer Dim frmStart As Starter = New Starter Application.Run(frmStart) Return 0 End Function End Module
As mentioned in our description, the calendar control displays the days of a selected month. The control also displays the remaining days, if any, of the first week of the currently selected month; that is, the days of the previous month that share the week with the first day of the first week of the selected month. The control also displays the first days of the subsequent month that share the week with the last day of the current month.
To use the calendar control, the user can click a date, whether it a date from the current month or a day of the other (previous and next) month. When the user has clicked a date to select it, the control fires a DateSelected event. The DateSelected event is of type DateRangeEventArgs.
The user can also select a date using the keyboard. To do this, the user must first give focus to the control. This is possible by pressing Tab continuously until the control receives focus (or by clicking any date on the control. To select a date using the keyboard, the user can continually press one of the arrow keys (on the keyboard) until the desired date is selected.
You too can programmatically select a date on the calendar control. To do this, assign a valid DateTime value to both the SelectionStart and the SelectionEnd properties. Here is an example:
Imports System.Drawing Imports System.Windows.Forms Module Exercise Public Class Starter Inherits Form Private Calendar As MonthCalendar Dim components As System.ComponentModel.Container Public Sub New() InitializeComponent() End Sub Public Sub InitializeComponent() Calendar = New MonthCalendar Calendar.Location = New Point(10, 10) Controls.Add(Calendar) End Sub Private Sub FormLoaded(ByVal sender As Object, _ ByVal e As EventArgs) _ Handles Me.Load Calendar.SelectionStart = New DateTime(1988, 12, 5) Calendar.SelectionEnd = New DateTime(1988, 12, 5) End Sub End Class Function Main() As Integer Dim frmStart As Starter = New Starter Application.Run(frmStart) Return 0 End Function End Module
When a date has been selected, whether by the user (using the mouse or the keyboard) or by you (through code), the control fires a DateChanged event. The DateChanged event is of type DateRangeEventArgs.
The DateRangeEventArgs class is equipped with two properties: Start and End. When the user clicks a date, these two properties hold the date that was clicked. This means that you can use either of these properties to know the date that was clicked. Both the Start and the End properties are of type DateTime.
When the user clicks the calendar control, one date is selected. As mentioned in our description, you can give the control the ability to display more than one month. To make this possible, when creating the control, set its width to have enough space. In the same way, you can increase the height to display many months.
To select more than one date, the user can click one date, hold the mouse down, and drag to the left, the right, up or down:
The user can also select a range of dates using the keyboard or using a combination of the mouse and the keyboard. To do this, the user must first give focus to the control. To select a range of dates using the keyboard, the user can press and hold Shift, then press one of the arrow keys continually until the last date of the desired range is selected (in reality, we will see that there is a property that controls the maximum range of dates that can be selected). To select a range of dates using a combination of the mouse and keyboard, the user can click the first date, press and hold Shift, then click the last date.
After selecting the days, the starting date is stored in the SelectionStart property. The last date of the selection is stored in the SelectionEnd property. Both properties are of DateTime type. The range of the selected dates is stored in a SelectionRange value. SelectionRange is simply a class that can give you information about the beginning and the end of a selected range of dates.
To programmatically select a date, assign the starting to the SelectionStart property and assign the last date to the SelectionEnd property.
By default, the user can select only up to 7 days at a time. If you want the user to be able to select more or less days than that. Here is an example where the user have selected dates from the 11 to the 20th, that is 10 days:
If you configure the control to display more than one month, the user can select days from one month to another as long as the days are in a range. Here is an example of a calendar that displays two months and the user had selected dates from September 21st, 2007 to October 11th, 2007:
After selecting a range of dates, the control fires a DateChanged event, which is of type DateRangeEventArgs. We saw earlier that the DateRangeEventArgs class has two properties. The DateRangeEventArgs.Start property holds the starting date of the range that the user made. The DateRangeEventArgs.End holds the last date from the range that the user made.
To control the number of days you want the user to be able to select, change the value of the MaxSelectionCount property. The user cannot select more days than the MaxSelectionCount value but the user can select less.
The calendar control is a rectangular object without a border. After placing it on the form, it displays the current month and only one month. This is because, by default, its width and height are set enough to accommodate only one month.
To make it a highly visual object, a calendar control uses different colors to represent the background, week days, the background of the title bar, the text of the title bar, the text of the days of the previous month, and the text of the days of the next month.
As mentioned already, to change month and subsequently the year of the calendar, the user can click the buttons continuously. By default, the user can navigate from 1/1/1753 to 12/31/9998. If you want to limit the allowable dates beyond which the user should not navigate, use the MinDate and the MaxDate properties.
Under the title bar, the short names weekdays display, using the format set in Control Panel. In US English, the first day is usually Sunday. If you want to start with a different day, set the value using the FirstDayOfWeek property. The names of weekdays use the same color as the TitleBackColor property. Under the names of the week, there is a horizontal line used as the separator. By default, this line separator is painted in black but it uses the same color as the numeric values of the days of the selected month.
Besides the days of the currently selected month, the calendar control also displays one or more days of the previous month and one or more days of the subsequent month. These are referred to as trailing months or trailing days. These are dayts that don't belong to the currently selected month. These days display in a different color controlled by the TrailingForeColor property. By default, this color is set to GrayText:
Of course, you can programmatically change these colors. Although any color is allowed in any category, you should make sure that the calendar is still reasonably appealing and usable.
The calendar control is used to let the user know today's date in two ways. On the calendar, today's date is circled by an almost hand-drawn ellipse. In the bottom section of the calendar, today's date is also displayed as a sentence. If you want to display or hide the bottom label, set the ShowToday Boolean property accordingly. For example, to hide it, set this property to false. The presence or absence of this ellipse is controlled by the ShowTodayCircle Boolean property whose default value is True. If you set this property to False, today's would appear without the ellipse:
When a new calendar control is added to an application, it assumes today's date. If you want to change this date, use the TodayDate property.
To accentuate the importance of one or more days of a month, you can bold some days. To bold some days of the calendar, create an array that holds the days. To visually create the list of dates, on the form, click the calendar control. In the Properties window, click BoldDates and click the ellipsis of its field. This would open the DateTime Collection Editor. To add a date member, you can click Add. On the right side, there would be a field named Date. You can type the date or you can click the arrow of the field. This would display a calendar:
You can then select a date. In the same way, to complete the array, you can create the other dates you want. After creating the list, you can click OK.
To programmatically create the list of dates, create an array of DateTime values (each member of the array must be a recognizable DateTime value). Once the array is ready, assign it to the BoldDates property.
If you prefer the months bolded, assign the array to the MonthlyBoldedDates property.
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