Templates: Part I

Templates are used to specify the presentational layout of controls. A template can contain static text, components, or controls that contribute to the ultimate presentation of the associated control. By default, an instance of TTemplateControl or its subclass may automatically load and instantiate a template from a file whose name is the same as the control class name. For page templates, the file name suffix must be .page; for other regular template controls, the suffix is .tpl.

The template format is like HTML, with a few PRADO-specifc tags, including component tags, template control tags, comment tags, dynamic content tags, and dynamic property tags. .

Component Tags

A component tag specifies a component as part of the body content of the template control. If the component is a control, it usually will become a child or grand child of the template control, and its rendering result will be inserted at the place where it is appearing in the template.

The format of a component tag is as follows, <com:ComponentType PropertyName="PropertyValue" ... EventName="EventHandler" ...> body content </com:ComponentType> ComponentType can be either the class name or the dotted type name (e.g. System.Web.UI.TControl) of the component. PropertyName and EventName are both case-insensitive. PropertyName can be a property or subproperty name (e.g. Font.Name). Note, PropertyValue will be HTML-decoded when assigned to the corresponding property. Content enclosed between the opening and closing component tag are normally treated the body of the component.

It is required that component tags nest properly with each other and an opening component tag be paired with a closing tag, similar to that in XML.

The following template shows a component tag specifying the Text property and OnClick event of a button control, <com:TButton Text="Register" OnClick="registerUser" /> Note, property names and event names are all case-insensitive, while component type names are case-sensitive. Event names always begin with On.

Also note, initial values for properties whose name ends with Template are specially processed. In particular, the initial values are parsed as TTemplate objects. The ItemTemplate property of the TRepeater control is such an example.

To deal conveniently with properties taking take big trunk of initial data, the following property initialization tag is introduced, <prop:PropertyName> PropertyValue </prop:PropertyName> It is equivalent to ...PropertyName="PropertyValue"... in every aspect. Property initialization tags must be directly enclosed between the corresponding opening and closing component tag.

Component IDs

When specified in templates, component ID property has special meaning in addition to its normal property definition. A component tag specified with an ID value in template will register the corresponding component to the template owner control. The component can thus be directly accessed from the template control with its ID value. For example, in Home page's template, the following component tag <com:TTextBox ID="TextBox" Text="First Name" /> makes it possible to get the textbox object in code using $page->TextBox.

Template Control Tags

Initial values specified via the template control tag are assigned to the corresponding properties when the template control is being constructed. Therefore, you may override these property values in a later stage, such as the Init stage of the control.

Template control tag is optional in a template. Each template can contain at most one template control tag. You can place the template control tag anywhere in the template. It is recommended that you place it at the beginning of the template for better visibility.

Comment Tags

Comment tags are used to put comments in the template or the ultimate rendering result. There are two types of comment tags. One is like that in HTML and will be displayed to the end-users. The other only appear in a template and will be stripped out when the template is instantiated and displayed to the end-users. The format of these two comment tags is as follows,

Note, template comments (by <!-- ... --!>) cannot appear in a property value.

Include Tags

Since version 3.0.5, PRADO starts to support external template inclusion. This is accomplished via include tags, where external template files are specified in namespace format and their file name must be terminated as .tpl.

External templates will be inserted at the places where the include tags occur in the base template.

Note, nested template inclusion is not supported, i.e., you cannot have include tags in an external template.