Skip to main content

A Implementation - Strong Typed Models

After a year-long project of DD4T Java, where we developed version 2.0 of the framework, it is now time to do it all over again, this time in .NET. This is the first of a series of posts dedicated to implementing DD4T .NET.

DD4T Java v2.0 offers a few goodies that are currently not available in DD4T .NET (v1.31). For example strong type model support or a Model Factory.

I'm going to start with presenting a flavor of strong type models that can be used in your project. I initially went on and called them ViewModels, but in fact they are more like domain models. They are used as building blocks for creating the actual view models that the Views use.

As such, the domain models represent a one to one mapping of the Schema and the properties inside each model class represent fields in the Schema. They are strong typed because they follow the same types declared in the fields (numeric, text, Component Link, Keyword, etc). Multi-valued fields are represented as IList generics.

Let's take the following example and explain it in detail.

    public class Device : BaseModel
        public Banner Banner { get; set; }
        public IList<EmbeddedParagraph> Body { get; set; }
        public IList<BaseModel> RelatedItems { get; set; }
        public DeviceMetadata Metadata { get; set; }

        public class DeviceMetadata
            public double LegacyId { get; set; }
            public string ShortTitle { get; set; }
            public IList<IKeyword> Products { get; set; }
            public DateTime UpdateDate { get; set; }

        public Device(IComponent component) : base(component) { }

The Device model represents a direct mapping of the Schema Device and each property inside the model represents a field in the Schema. The simple types are Text (string), Numeric (double), Date (DateTime). Embedded fields, Component link fields and Multimedia links have their own domain model types, defined in their respective classes.

Property Banner represents a single-value Component link to another model based on Schema Banner. However, property RelatedItems is a multi-value Component link that in the Schema it is configured to allow more than one possible type. Hence, the type of the IList generic is BaseModel, which simply represents the base class each domain model inherits from. More about the BaseModel, below.

Text fields in a Schema that represent Keywords in a Category are mapped to DD4T.ContentModel.IKeyword properties in the model.

I chose to implement metadata fields as properties of an inner class nested inside each domain model (i.e. DeviceMetadata in the example above).

Embedded fields (e.g. Body) have their own domain model class, only they don't represent a Component like the Device model does. They lack the constructor that take an IComponent parameter as well. Below is such a embedded domain class:

    public class EmbeddedParagraph : BaseModel
        public string Heading { get; set; }
        public string Body { get; set; }

Multimedia Schemas map to similar domain models, but with a little twist -- they don't contain any fields/properties; they only contain metadata fields/properties and a DD4T.ContentModel.IMultimedia property to hold the multimedia metadata itself.

    public class Image : BaseModel
        public IMultimedia Multimedia { get; set; }
        public ImageMetadata Metadata { get; set; }

        public class ImageMetadata
            public string AltText { get; set; }
            public string TitleText { get; set; }

        public Image(IComponent component) : base(component) { }

The BaseModel class declares a few base properties, such as Id, Schema, or model Title. It also handles some basic Component Link resolving (resolving the URL of a Page where this domain model appears on -- but more about that in another post).

    public class BaseModel : IComparable<BaseModel>
        public string Id { get; set; }
        public ISchema Schema { get; set; }
        public string Title { get; set; }

        public BaseModel() { }

        public BaseModel(IComponent component)
            Id = component.Id;
            Schema = component.Schema;
            Title = component.Title;


Popular posts from this blog

Running sp_updatestats on AWS RDS database

Part of the maintenance tasks that I perform on a MSSQL Content Manager database is to run stored procedure sp_updatestats . exec sp_updatestats However, that is not supported on an AWS RDS instance. The error message below indicates that only the sa  account can perform this: Msg 15247 , Level 16 , State 1 , Procedure sp_updatestats, Line 15 [Batch Start Line 0 ] User does not have permission to perform this action. Instead there are several posts that suggest using UPDATE STATISTICS instead: I stumbled upon the following post from 2008 (!!!), , which describes a way to wrap the call to sp_updatestats and execute it under a different user: create procedure dbo.sp_updstats with execute as 'dbo' as

Content Delivery Monitoring in AWS with CloudWatch

This post describes a way of monitoring a Tridion 9 combined Deployer by sending the health checks into a custom metric in CloudWatch in AWS. The same approach can also be used for other Content Delivery services. Once the metric is available in CloudWatch, we can create alarms in case the service errors out or becomes unresponsive. The overall architecture is as follows: Content Delivery service sends heartbeat (or exposes HTTP endpoint) for monitoring Monitoring Agent checks heartbeat (or HTTP health check) regularly and stores health state AWS lambda function: runs regularly reads the health state from Monitoring Agent pushes custom metrics into CloudWatch I am running the Deployer ( installation docs ) and Monitoring Agent ( installation docs ) on a t2.medium EC2 instance running CentOS on which I also installed the Systems Manager Agent (SSM Agent) ( installation docs ). In my case I have a combined Deployer that I want to monitor. This consists of an Endpoint and a

Debugging a Tridion 2011 Event System

OK, so you wrote your Tridion Event System. Now it's time to debug it. I know this is a hypothetical situtation -- your code never needs any kind of debugging ;) but indulge me... Recently, Alvin Reyes ( @nivlong ) blogged about being difficult to know how exactly to debug a Tridion Event System. More exactly, the question was " What process do I attach to for debugging even system code? ". Unfortunately, there is no simple or generic answer for it. Different events are fired by different Tridion CM modules. These modules run as different programs (or services) or run inside other programs (e.g. IIS). This means that you will need to monitor (or debug) different processes, based on which events your code handles. So the usual suspects are: dllhost.exe (or dllhost3g.exe ) - running as the MTSUser is the SDL Tridion Content Manager COM+ application and it fires events on generic TOM objects (e.g. events based on Tridion.ContentManager.Extensibility.Events.CrudEven