Missing and empty data values

When you submit data for a control, some of the control data might not be available. For a control with missing data, you can do one of the following:

• Exclude the ItemData element for a control for which data was not collected.
• Set the IsNull attribute for the control to Yes if data was collected but then cleared, or to clear data for the control.

  Note:

  If you specify the IsNull attribute, you cannot specify the Value attribute for the control.