Databases Reference
In-Depth Information
FIGURE 7.1
Metadata API at a glance.
At the highest level, the Metadata API represents a
meta model
—metadata information
specific to Dynamic Data. This information is most relevant to Dynamic Data web applica-
tions and is exposed using APIs (classes, properties, and methods) designed specifically for
this purpose. However, presenting
all
information required by Dynamic Data applications
in special APIs would mean recreating
System.Reflection
and
System.ComponentModel
APIs, which are well designed and well known, even if not very easy to use. Instead,
Dynamic Data tries to strike a balance between creating an API relevant to dynamic web
applications and reusing the existing .NET framework APIs.
The next level down includes the metadata information provided by the
data model
. The
data access frameworks, such as LINQ to SQL and Entity Framework, provide metadata
information you could use to discover entity classes and access their data. Dynamic Data
wraps these APIs in a framework-agnostic
provider model
defined in the
System.Web.
DynamicData.Providers
namespace. The provider model is also available through the
Metadata API. However, this is an advanced topic that requires special attention. You can
find a detailed discussion of this subject in Chapter 13, “Building Dynamic List Pages.”
At the lowest level of abstraction is metadata information provided by the .NET runtime.
The
Type
class in the
System
namespace provides information about classes, properties,
methods, and attributes; it is an incredibly powerful but low-level tool. The
TypeDescriptor
class in
the System.ComponentModel
namespace works at a slightly higher level and has
built-in understanding of data annotations. However, using these APIs directly in a
