14.4.4. Application Code
Most VSPX controls will support XML children specifying SQL code to run at various points of the page processing cycle. The elements are:
| v:before-data-bind |
| v:after-data-bind |
| v:before-post |
| v:before-render |
These elements will have a script tag as unique child, most often containing a CDATA section for escaping the SQL text.
Additionally, most attributes of VSPX elements can have a SQL expression
evaluated at initialization, pre data bind or after data bind time, as
the case may be, depending on the attribute and its value.
An attribute value beginning with "--"
indicates evaluation on the initialization or the descending edge of the data
bind pass. An attribute value indicating "--after"
specifies that the value is calculated on the returning edge of recursion of the data bind pass.
Arbitrary HTML text may contain attributes with a data bound value. The
attributes should be in the XHTML namespace and have a text beginning with
"--"
. The expression will be evaluated at
render time, where the control
variable refers to the
enclosing VSPX template control, e.g. the page instance when at top level.
VSP Compatibility and In-Line SQL
Arbitrary HTML text may contain <?vsp ?>, <?V ?> (equivalent of <?= VSP notation) and <?U ?> (equivalent of <?/ VSP notation) processing instructions. The code in question will be evaluated during the render pass, with control set to the closest enclosing VSPX control. Please note that the <?= and <?/ VSP shortcuts cannot be used inside VSPX pages as they are not valid processing-instructions.
VSPX maintains backward compatibility with VSP through supporting the
same processing instructions, but additionally requires the page source to be
well formed XML. VSP pages which are well formed in XML terms will run as
such under with the VSPX extension, with the addition of the
v:page
top level element.
The <?vsp ?> processing instruction expects a SQL statement. The statement can be a compound statement ending in another <?vsp ?> processing instruction at the same nesting level under the same parent tag. The other pi's <?V and <?U expect a SQL expression.
![[Note]](images/note.png)
|
Note: |
|---|---|
|
<?V ?> is not permitted inside attributes without quotation,
as this is not well formed XML. When quoted, this notation in attributes
has no special effect, hence the convention about the leading
|