The MessageHeader concept in our DSL has an attribute “SchemaLocation” (the same is true for Message and DataContract). This property is a reference to the XSD description of the MessageHeader. Another property of the Message concept is the “Namespace” property. The value of this property is used in the WSDL that is generated out of the Domain model of our DSL. In an attempt to make our DSL as user friendly as possible I decided to set the “Namespace” property automatically as soon as the “SchemaLocation” is populated.
To make this possible I wrote a propagation rule (one of the customization features of the DSL Tools) to make this happen.
Below you can see the code that is needed for a propagation rule. I stored this code in a separate .cs file in a folder called “custom” that I created in the designer project. The rule inherits from “ChangeRule”. The implementation isn’t that difficult (note: just demo code)
[RuleOn(typeof(OurCompany.Design.ServiceDescription.DomainModel.MessageHeader),
FireTime = TimeToFire.TopLevelCommit)]
public sealed class DomainModelMessageHeaderPropertiesChangesRule : ChangeRule
{
public override void ElementAttributeChanged(ElementAttributeChangedEventArgs e)
{
// store the Namespace in
string messageHeaderNamespace;
OurCompany.Design.ServiceDescription.DomainModel.MessageHeader messageHeader =
e.ModelElement as OurCompany.Design.ServiceDescription.DomainModel.MessageHeader;
if (messageHeader != null)
{
if (e.MetaAttribute.Id ==
OurCompany.Design.ServiceDescription.DomainModel.MessageHeader.SchemaLocationMetaAttributeGuid)
{
if (!String.IsNullOrEmpty(messageHeader.SchemaLocation))
{
// helper code to retrieve the Namespace from the XSD
ServiceDescriptionEngine.GetSchemasFromXsd(messageHeader.SchemaLocation, out messageHeaderNamespace);
// set the value of the Namespace property
messageHeader.Namespace = messageHeaderNamespace;
}
}
}
}
}
Because the code that actually retrieves the “Namespace” out of the XSD file is stored in another assembly that isn’t part of the DSL assemblies, I had to add the assembly to the GAC to make it work.
To make sure the rule gets fired we need to add a variable to the “GeneratedMetaModelTypes” class. This class is reflected on to dynamically load rules. The variable is the reference to the new propagation rule described above. The following code snippet will do the trick.
Internal static partial class GeneratedMetaModelTypes
{
internal static Type DomainModelMessageHeaderPropertiesChangesRule =
typeof(DomainModelMessageHeaderPropertiesChangesRule);
}
As you can see in the image below (I know this image doesn’t prove a lot!) the “Namespace” property gets set after we populate the “SchemaLocation” property of the MessageHeader with a valid value.
To be continued...