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Using the Preview view of a DataWindow object
160 DataWindow .NET
DataWindow Designer
uses data caching
When DataWindow Designer first retrieves data, it stores the data internally.
When it refreshes the Preview view, DataWindow Designer displays the stored
data instead of retrieving rows from the database again. This can save you a lot
of time, since data retrieval can be time consuming.
How using data from
the cache affects you
Because DataWindow Designer accesses the cache and does not automatically
retrieve data every time you preview, you might not have what you want when
you preview. The data you see in preview and the data in the database can be
out of sync.
For example, if you are working with live data that changes frequently or with
statistics based on changing data and you spend time designing the
DataWindow object, the data you are looking at may no longer match the
database. In this case, retrieve again just before printing.
Explicitly retrieving
data
You can explicitly request retrieval at any time.
❖ To retrieve rows from the database:
• Do one of the following:
• Click the Retrieve button in the PainterBar.
• Select Rows>Retrieve from the menu bar.
• Select Retrieve from the Preview view’s pop-up menu.
Supplying argument values or criteria
If the DataWindow object has retrieval arguments or is set up to prompt
for criteria, you are prompted to supply values for the arguments or to
specify criteria.
DataWindow Designer retrieves the rows. As DataWindow Designer
retrieves, the Retrieve button changes to a Cancel button. You can click the
Cancel button to stop the retrieval at any time.
Sharing data with the
Data view
The Data view displays data that can be used to populate a DataWindow object.
When the ShareData pop-up menu item in the Data view is checked, changes
you make in the Data view are reflected in the Preview view and vice versa.
Other options that
affect retrieval
These other options can affect retrieval:
• Retrieve Rows As Needed Lets you specify that only the rows needed
to display the current portion of the DataWindow object should be
retrieved. When you scroll downward, additional rows are retrieved. This
can speed up reporting in certain situations.
See “Retrieving rows as needed” on page 188.