Databases Reference
In-Depth Information
The
MetaModel
class serves as a root access point for Dynamic Data components to find
information about the tables. In particular, the dynamic URL routing functionality relies
on the
MetaModel
to determine if the incoming request is valid and route it to the appro-
priate page template. Although multiple instances are supported, a typical Dynamic Data
application contains a single
MetaModel
, created and initialized in the
Global.asax
as
shown in the following example:
public class Global : HttpApplication
{
public static readonly MetaModel DefaultModel = new MetaModel();
void Application_Start(object sender, EventArgs e)
{
DefaultModel.RegisterContext(typeof(NorthwindEntities));
}
}
Data Model Registration
The
MetaModel
instance is initially empty and requires a call to one of the
RegisterContext
methods to populate it with
MetaTable
objects:
public void RegisterContext(Type contextType);
public void RegisterContext(Func<object> contextFactory);
public void RegisterContext(DataModelProvider dataModelProvider);
In the simplest case, you can initialize the
MetaModel
by calling the
RegisterContext
method that takes a type object such as
typeof(NorthwindEntities)
in the example just
shown.
MetaModel
has built-in support for Entity Framework and LINQ to SQL and expects
a type derived from
ObjectContext
or
DataContext
, respectively. Using this type, Dynamic
Data creates a new instance of the context class whenever a context is required at run
time. Any context class registered this way must have a default constructor.
If your context class doesn't have a default constructor or if you need to perform addi-
tional initialization steps, you can use the
RegisterContext
method that takes a context
factory
delegate
as a parameter:
public static readonly MetaModel DefaultModel = new MetaModel();
void Application_Start(object sender, EventArgs e)
{
DefaultModel.RegisterContext(this.CreateContext);
}
private object CreateContext()
{
NorthwindEntities context = new NorthwindEntities();
