Adding Metadata to Entities in The Data Model

Gil Fink — Thu, 20 Jan 2011 19:28:37 GMT

Adding Metadata to Entities in The Data Model

Sometimes I’m being asked how to add metadata to a generated entity in Entity Framework. This metadata can be data annotation or other attributes which can help the developer during runtime. One answer that I give is to edit the T4 template in order to add the attributes. This solution can be combined with the building of an extension to Entity Framework designer which can add more details to the EDM. But it can take some time to develop. Another solution is to create a MetadataType for the entity and use the entity’s partial class behavior to add this type. This post will show you the second solution.

Adding Metadata to a Generated Entity

In the example I’m going to use the following simple entity:

This type is part of a Dynamic Data site and the requirements for it are not to show the TypeID and that the Url needs to be up to 100 characters. Since Dynamic Data work with Data Annotations I want to add this metadata to the entity. But the problem is that the entity is generated by Entity Framework code generation. So how can I add the annotations? using the MetadataType attribute. The MetadataType is an attribute that is part of the System.ComponentModel.DataAnnotations assembly. It indicates that the a data model class has an associated metadata class. The MetadataType attribute gets a type parameter to specify which type is holding the metadata for the class. We can use the fact that the entity is generated as partial class and add the MetadataType attribute to it. Lets look at an example of how to use the MetadataType attribute:

       public class CRMTypeMetadata

      {

          [ScaffoldColumn(false)]

          public int TypeID { get; set; }

          [StringLength(100)]

          public string Url { get; set; }

      }

      [MetadataType(typeof(CRMTypeMetadata))]

      public partial class CRMType

      {

      }

The first thing to notice in the example is that I’ve created a public class by the name CRMTypeMetadata which hold the properties annotated with the relevant attributes. The Metadata postfix in the class name is a convention that I encourage you to use. After I create the metadata class all I need to do is to create a partial class for the generated entity and annotate it with the MetadataType attribute. The MetadataType attribute will get as a parameter the type of the metadata type which is CRMTypeMetadata in the example. That is all.
Now the expected behavior was achieved.

Summary

One of the solutions to add metadata to entities in the Entity Data Model is by using the MetadataType attribute. It is very simple to use and can help you in frameworks like ASP.NET MVC, Dynamic Data, WCF Ria Services and more.

Create Your First Dynamic Data Entities Web Application

Gil Fink — Wed, 07 Oct 2009 11:45:12 GMT

Create Your First Dynamic Data Entities Web Application

Two weeks ago I was
asked if there is a way
to build a web back office
quickly. One thing that
popped into my mind was
the new ASP.NET Dynamic Data
framework that was shipped with
Visual Studio 2008 SP1. This post is the same introduction that I
made to the team members that asked me the question. Since
there weren’t any customizations needed in the back office they
needed the result was a standing back office in 5 minutes. That is
very productive.

Creating the Dynamic Data Application

The first thing to do is to create the Dynamic Data application.
This is a very easy job since we can pick one of Dynamic Data templates
which will generate the site. In Visual Studio choose File menu
and New –> Project or New –> Web Site and then choose one of
Dynamic Data templates on the Web templates. The options are
Dynamic Data Web Application which will generate a general Dynamic
Data application or Dynamic Data Entities Web Application which is
more appropriate to use with Entity Framework or LINQ to SQL.
I chose the second:

After pushing the OK button Visual Studio generates the Dynamic Data
application and we are clear to go. The result will look like:

Adding ADO.NET Entity Framework to the Application

When we have the application at hand now we need to create the Entity
Framework model. This is very straight forward. You can choose to create a
different class library and put the model there (the preferred way) or you
can just put the model in the created project. For the simplicity of this demo
I chose the second option and the result is the model I’m using in all my demos:

Since this is only a demo for Dynamic Data and not for Entity Framework
I’m not showing how to create the model. If you seek information about how
to create an Entity Framework EDM I encourage you to read my
ADO.NET Entity Framework Tutorials series and in particularly the post
Entity Data Model (EDM) In Entity Framework.

Integrating the Context to the Dynamic Data Application

Now that we have the application and the Entity Framework model
it is time to combine them both. We do so by opening the Global.asax
file and in the RegisterRoutes we register the context using the model
object’s RegisterContext method. Pay attention that I set the
ScaffoldAllTables to true in order to show all the entities in my context.
If you want to show only part of them set the ScaffoldAllTables to false
and for every entity you want to show create a partial class and add there
the [Scaffold(true)] attribute.
After I register the context the RegisterRoutes will look like:

     public static void RegisterRoutes(RouteCollection routes)

    {

        MetaModel model = new MetaModel();

        model.RegisterContext(typeof(SchoolEntities), new ContextConfiguration() { ScaffoldAllTables = true });

        routes.Add(new DynamicDataRoute("{table}/{action}.aspx")

        {

            Constraints = new RouteValueDictionary(new { action = "List|Details|Edit|Insert" }),

            Model = model

        });

    }

That is all. Now we can run the Dynamic Data application and use it as
a web back office for our application.
My application looks like:

Summary

Lets sum up, I showed in this post how in 5 minutes of work you
can create a working web back office application. The Dynamic
Data framework can be very useful in lots of scenarios such as creating
web back office for example.I suggest to give it a try and to find out
were it can fit your requirements.

Gil Fink's Blog : ADO.NET, Dynamic Data

Adding Metadata to Entities in The Data Model

Adding Metadata to Entities in The Data Model

Adding Metadata to a Generated Entity

Summary

Create Your First Dynamic Data Entities Web Application

Create Your First Dynamic Data Entities Web Application

Creating the Dynamic Data Application

Adding ADO.NET Entity Framework to the Application

Integrating the Context to the Dynamic Data Application

Summary