Overview

When you bind your chart control to a datasource, it automatically detects the data type present, and performs all of the necessary conversions for you. This is especially important when you are working with DateTime data types. This article discusses how to work with dates, and the DateTime data type.

Working With DateTime Data

To enable DateTime support, a Series object's XValueType property, YValueType property, or both must be changed from their default Auto value to a value of DateTime. This allows dates to be entered at design-time using a string format like "11/12/2001" (in the short date format defined by the regional settings). Use the Advanced Properties screen of the charting web part control to set the above named properties.

 

Follow these steps to set the XValueType and YValueType properties:

1. Click the Advanced Properties button on the web part toolbar.
2. Choose Series from the Advanced Properties left-hand navigation pane.
3. In the Data category, set the XValueType and YValueType properties to DateTime.
4. Click Finish to complete the task and exit the Advanced Properties screen.

 

Setting these properties also lets you preview and format any existing date labels. If no data points are provided at design-time "dummy" data points will be generated using a nominal date as the starting point.

DateTime formatting for axis labels is done using the Axis' LabelStyle property. DateTime formatting for data point labels is done using the LabelFormat property of Series, and DataPoint objects. There is also design-time support for DateTime formatting using the Label Format dialog.

Once the Series object's XValueType or YValueType property is set, an axis can have its Minimum and Maximum properties set to DateTime values.

 

At run-time values can be converted from doubles to dates using the FromOADate and ToOADate functions of the DateTime class.

When data points, who have only their YValues set and no XValues specified, are added to a chart using an x-axis LabelStyle.IntervalType property setting of DateTime, the date for labels will be interpreted as a Double with a value of zero. This equates to a date of "12/30/1899 12:00 AM". To avoid this situation, either set a DateTime X value for the data points, or refrain from specifying the XValueType of the plotted series as DateTime.

There may be instances when axis labels, grid lines, or tick marks will not align with the data that you are presenting in the chart. For example, when the first data point is the 15th of January, yet the chart displays the first axis label, grid line, and tick marks as January 1. To align these chart objects (Axis Labels, Grid Lines, Tick Marks, and Strip Lines) use the IntervalOffset and IntervalOffsetType properties. This will allow you to offset the starting points of all these objects. The value of the offset is determined by the IntervalOffsetType (Minutes, Hours, Days, Weeks, etc.), and can be set to the same value as the IntervalType property.

Date and Time Formatting

Both standard and custom DateTime formats can be used for labels. It is worthy to note that both types of formats are influenced by the Regional Options settings in Windows control panel.

 

 

Standard Formats

Standard DateTime formats are set using specifiers which represents a formatted date or time. The following is a listing of the more common formats along with a brief description and an example of their effect on a date or time:

Format Specifier	Description	Example
d	Short date pattern.	6/13/2003
D	Long date pattern.	Thursday, June 13, 2003
t	Short time pattern.	12:00 AM
T	Long time pattern.	12:00:00 AM
f	A full date/time pattern that uses a short time.	Thursday, June 13, 2003 12:00 AM
F	A full date/time pattern that uses a long time.	Thursday, June 13, 2003 12:00:00 AM
g	A general date/time pattern that uses a short time.	6/13/2003 12:00 AM
G	A general date/time pattern that uses a long time.	6/13/2003 12:00:00 AM

 

All of the above format specifiers can be set using Step 3 of the Customization Wizard.

 

Follow these steps to set a format specifier for a DateTime values that exist on the Y-axis:

1. Choose Customization Wizard from the web part dropdown menu.
2. Choose Step 3:Chart Element Properties from the wizard's let-hand navigation pane.
3. Choose the Axes and GridLines tab, and go to the Y Axis and Grid Lines section shown in Figure 1 below.

    

   Figure 1: You can access the Format Picker window by clicking on the dropdown icon.

    

4. Choose a format from the Dundas Format Picker window, and click OK to apply it.
5. Click Finish to complete this task, and exit the wizard.

Custom Formats

Custom DateTime formats are also set using specifiers, and should be set using at least two characters. The following is a listing of the more common custom formats, along with a brief description:

Format Specifier	Description	Example
dd	Displays the current day of the month as a number.	07
ddd	Displays the current day of the month as an abbreviated word.	Thu
dddd	Displays the current day of the month as the full word.	Thursday
MM	Displays the current month as a number.	06
MMM	Displays the current month as an abbreviated word.	Jun
MMMM	Displays the current month as a full word.	June
yy	Displays the year as an abbreviation.	02
yyyy	Displays the full year.	2003

 

All of the custom formats listed in the table above can be entered directly into any one of the Format fields shown in Step 3 of the Customization Wizard.

See Also

 

 

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