Building Custom Forms - ASP.NET Dynamic Data - page 318

LISTING 10.8 Continued
base.OnPreRender(e);
var fieldTemplate = this. FindFieldTemplate (this.DataField)
as FieldTemplateUserControl;
if (fieldTemplate != null && fieldTemplate.DataControl != null)
{
this.AssociatedControlID =
fieldTemplate.DataControl.GetUniqueIDRelativeTo(this);
}
}
}
}
Most of the work in UnleashedLabel is done by the OnInit method. It uses the
FindMetaTable extension method defined in the DynamicDataExtensions class to find the
MetaTable object associated with the FormView or GridView hosting this control. As you
recall from Chapter 7, “Metadata API,” all page templates in Dynamic Data have to associ-
ate a MetaTable object with their databound controls either with the help of a
DynamicDataManager control or explicitly in code-behind. The UnleashedLabel control
takes advantage of this fact similar to how the DynamicControl does.
Having obtained the MetaTable object, the OnInit method calls its GetColumn method to
find the MetaColumn object describing the entity property based on the DataField property
supplied in markup. After the MetaColumn object has been retrieved, its DisplayName prop-
erty value is then used to initialize the Text property of the label.
Aside from having to find the MetaColumn object programmatically, the OnInit method in
UnleashedLabel performs the same function as the Label_Init event handler in the
dynamic entity template shown in Listing 10.6; it initializes the label text based on the
display name of the entity property. Likewise, the OnPreRender method is very similar to
the Label_PreRender event handler in that it associates the label with the data control
generated by the field template. The only significant difference here is that this code relies
on the FindFieldTemplate extension method defined in the DynamicDataExtensions class
to find the field template instead of accessing the corresponding DynamicControl directly.
NOTE
To use this control in mar kup, you could register it in the various pages and user
controls individually. However, because the sample solution uses it pervasively, it
makes sense to register it globally by adding the following line to the
System.Web/Pages/Controls section of the Web.config file:
<add tagPrefix=”unl”
assembly=”Unleashed.DynamicData”
namespace=”Unleashed.DynamicData “/>