Building Dynamic List Pages - ASP.NET Dynamic Data - page 422

[MetadataType(typeof(Metadata))]
partial class Product
{
private abstract class Metadata
{
[UIHint(“Text”, null, “Columns”, 100)]
[ FilterUIHint(“Text”, null, “Columns”, 100 )]
public object ProductName { get; set; }
}
}
Just like the UnleashedControl , which was extended in Chapter 11 to automatically
initialize matching public properties of the field templates based on the control parame-
ters specified in the UIHintAttribute , the UnleashedFilter initializes public properties of
the filter templates based on the information specified in the FilterUIHintAttribute ,
such as the Columns property in this example.
This chapter centers discussion on eliminating some of the shortcomings in Dynamic Data
that make building metadata-driven list pages more difficult than they really need to be. It
also continues the discussion of how to build list pages that display and allow searching
information from multiple related entities, this time dynamically. To accomplish these
goals, the sample solution extends the metadata information, which was reviewed in
Chapter 7, “Metadata API.”
Extending Filter Lookup Rules
As you might recall from a discussion in Chapter 3, “Field Templates,” Dynamic Data uses
a sophisticated algorithm to locate field templates based on the metadata information
describing entity properties. It first checks the entity property for presence of the
UIHintAttribute , which can specify the name of a field template explicitly. If the prop-
erty does not have a UI hint, Dynamic Data then checks it for the DataTypeAttribute ,
which can specify a business-level name of the property type, such as EmailAddress or
Date , and look for field templates with the matching name. In the absence of a high-level
data type, Dynamic Data uses a low-level type of the entity property, such as String or
DateTime , to look for the matching field template. If a direct match is not immediately
available, Dynamic Data uses a fallback algorithm to try more and more generic types,
such as going from Float to decimal to string.
The lookup algorithm used for field templates makes it easier to develop dynamic pages
because it significantly reduces the amount of additional data annotation attributes
needed in the entity model. Unfortunately, Dynamic Data does not implement the same
fallback-based rules for locating filter templates. In fact, it hard-codes the lookup rules to
the three types of filter templates that come with it out of the box—Boolean,
Enumeration, and ForeignKey. For all other types of properties— String , Int32 , DateTime ,
and so on—the filter template name has to be specified explicitly.