Set a key/id to a Workflow - workflow

Question

New to Workflow Foundation, so it may be a basic question for many of you.
I have a workflow designer (client) /server application.
In the designer I can upload workflows to the server , which stores them in the DB. The designer can request to download a workflow from the server. Once downloaded , we can modify it in the designer and upload it again.
To be able to do that I need to add some sort of ID/Key to the workflow.
What's the best way to do that?
I was thinking about adding a property to the ActivityBuilder, but doing that adds it to the argument list, which doesn't seem right...
Any help would be much appreciated
Hi #Will, I gave it a go attaching the property to Activities but I can not get it working. I'm not using any models like WorkflowRecord, it's just a basic desginer.
I use _workflowDesigner.Save(path); to save it or _workflowDesigner.Load(path); to load it.
I create and add the attached property
attachProp = new AttachedProperty<int?>()
{
Name = "Key",
IsBrowsable = true,
Getter = (modelItem) => 5,
Setter = ((modelItem, keyValue) => modelItem.Properties["Key"].SetValue(keyValue)),
OwnerType = typeof(Activity)
};
_workflowDesigner.Context.Services.GetService<AttachedPropertiesService>().AddProperty(attachProp);
If I try to access the attached property, it throws me an exception (doesn't contain a definition for key)
dynamic mainActivity = ((_workflowDesigner.Context.Services.GetService<ModelService>().Root.GetCurrentValue() as ActivityBuilder).Implementation as Activity);
int? testValue = mainActivity.Key; //Exception, Activity' does not contain a definition for 'Key'
I read through this [post] (http://blogs.msdn.com/b/kushals/archive/2010/01/04/base-designer-with-additional-adornments.aspx) to add the attach property to the activity

Answer 1

Attached properties, via the AttachablePropertyServices Class.
public class WorkflowRecord
{
static AttachableMemberIdentifier Id =
new AttachableMemberIdentifier(typeof(Guid), "Id");
public static object GetCommentText(object instance)
{
object viewState;
AttachablePropertyServices.TryGetProperty(instance, Id, out viewState);
return viewState;
}
public static void SetCommentText(object instance, object value)
{
AttachablePropertyServices.SetProperty(instance, Id, value);
}
}
You can use this to get or set your database Id on an instance of the workflow, and it will be serialized/deserialized to/from xaml.
<Activity
xmlns:me="clr-namespace:Herp;assembly=derp"
me:WorkflowRecord.Id="This is a guid lol"
x:HideAdditionalAttributesBecauseThisIsAnExample="true" />
For more info, read this blog post on msdn