Building Dynamic List Pages - ASP.NET Dynamic Data - page 443

FilterUIHintAttribute to the Country property of the Product entity class, as shown in
the following example:
partial class Product
{
[UIHint(“Parent”, null, “DisplayField”, “Country”)]
[FilterUIHint(“Parent”, null, “DisplayField”, “Country”)]
public string Country { get { return this.Supplier.Country; } }
}
From the compiler standpoint, nothing prevents you from using the Parent field and filter
templates this way; however, code in these templates currently assumes that they are asso-
ciated with a foreign key property. Although Country, the custom property you created, uses
the Supplier foreign key property internally, this information is not immediately available
to the template. You can provide the missing information by passing an additional control
parameter, ForeignKeyField , with the name of the foreign key property, as shown next:
[UIHint(“Parent”, null,
“ForeignKeyField”, “Supplier”,
“DisplayField”, “Country”)]
[FilterUIHint(“Parent”, null,
“ForeignKeyField”, “Supplier”,
“DisplayField”, “Country”)]
public string Country { get { return this.Supplier.Country; } }
To take advantage of the new control parameter, the Parent templates need to be modi-
fied. The code snippet that follows shows how to extend the Parent field template to
define a public property called ForeignKeyField , matching the name of the control para-
meter specified in the UIHintAttribute and replacing the ForeignKeyColumn property to
locate the foreign key column based on its name. If the ForeignKeyField was not speci-
fied, the property falls back to the inherited implementation, which assumes that the
template is associated with a foreign key property. The filter template can be extended in
the same way; you can see its implementation in the source code that accompanies the
book:
public partial class ParentFieldTemplate : UnleashedFieldTemplate
{
private MetaForeignKeyColumn foreignKeyColumn;
public string ForeignKeyField { get; set; }
public new MetaForeignKeyColumn ForeignKeyColumn
{
get
{
if (this.foreignKeyColumn == null)
{