Activities are always collapsed in rehosted designer

I'm trying to rehost the designer, but every time I slap a workflow into the designer:

_workflowDesigner = new WorkflowDesigner();
// added to UI here
Properties.Content = _workflowDesigner.PropertyInspectorView;
_workflowDesigner.Load(myWorkflowInstance);

where myWorkflowInstance is a workflow defined in a referenced assembly. I have done the magic Register to get the default activity metadata registered:

new DesignerMetadata().Register();

and I've registered all my custom NativeActivities:

public static void Register(IEnumerable<Type> activityTypes)
{            
    // activityTypes are all my custom NativeActivities
    // and all workflows (root of System.Activities.Activity)
    var builder = new AttributeTableBuilder();
    var attrGroups =
        from x in activityTypes
        from y in x.GetCustomAttributes(true).OfType<Attribute>()
        group y by x into g 
        select g;

    foreach (var typeGroup in attrGroups)
        builder.AddCustomAttributes(typeGroup.Key, typeGroup.ToArray());
    MetadataStore.AddAttributeTable(builder.CreateTable());
}

yet, when I load an activity in开发者_如何转开发 the designer this is what I get:

What am I missing here?

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I'm thinking it has something to do with the fact that these workflows are compiled and only exist within the Implementation property of an Activity...

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Is your workflow instance wrapped in an ActivityBuilder?

Update: Investigating a little further here I found one possible solution using the WorkflowInspectionServices.

var activities = WorkflowInspectionServices.GetActivities(new DemoWorkflow());
designer.Load(activities.First());

---

A bit of reflector and reflection has led me to this travesty:

var impl = (typeof(DemoWorkflow)
            .GetProperty("Implementation", 
                         BindingFlags.NonPublic | BindingFlags.Instance)
            .GetValue(new DemoWorkflow(), new object[0]) 
            as System.Func<System.Activities.Activity>)();

_workflowDesigner.Load(new ActivityBuilder { Implementation = impl });

Is this it? Seriously? I feel sick knowing that I wrote that. Dirty.

I noticed in reflector that the xaml for the workflow actually is embedded in the assembly in a resource stream:

but all attempts to use this failed.

var target = typeof(DemoWorkflow);
var name = string.Format("{0}.obj.Debug.{1}.g.xaml", 
                         target.Assembly.GetName().Name, 
                         target.Name);
Activity derp = null;
using (var stream = assy.Assembly.GetManifestResourceStream(name))
{
    var reader = new XamlXmlReader(stream, new XamlSchemaContext());
    // throws an exception as the property Implementation is in the xaml;
    // it is protected and cannot be set, so deserialization blows up
    derp = ActivityXamlServices.Load(reader);
}

I don't see any other option at this point.