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

Scaling Policies

This post is part of a bigger topic Autoscaling Publishers in AWS . In a previous post we talked about the Auto Scaling Groups , but we didn't go into details on the Scaling Policies. This is the purpose of this blog post. As defined earlier, the Scaling Policies define the rules according to which the group size is increased or decreased. These rules are based on instance metrics (e.g. CPU), CloudWatch custom metrics, or even CloudWatch alarms and their states and values. We defined a Scaling Policy with Steps, called 'increase_group_size', which is triggered first by the CloudWatch Alarm 'Publish_Alarm' defined earlier. Also depending on the size of the monitored CloudWatch custom metric 'Waiting for Publish', the Scaling Policy with Steps can add a difference number of instances to the group. The scaling policy sets the number of instances in group to 1 if there are between 1000 and 2000 items Waiting for Publish in the queue. It also sets the

Toolkit - Dynamic Content Queries

This post if part of a series about the  File System Toolkit  - a custom content delivery API for SDL Tridion. This post presents the Dynamic Content Query capability. The requirements for the Toolkit API are that it should be able to provide CustomMeta queries, pagination, and sorting -- all on the file system, without the use third party tools (database, search engines, indexers, etc). Therefore I had to implement a simple database engine and indexer -- which is described in more detail in post Writing My Own Database Engine . The querying logic does not make use of cache. This means the query logic is executed every time. When models are requested, the models are however retrieved using the ModelFactory and those are cached. Query Class This is the main class for dynamic content queries. It is the entry point into the execution logic of a query. The class takes as parameter a Criterion (presented below) which triggers the execution of query in all sub-criteria of a Criterio

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