Activities are always collapsed in rehosted designer

Question

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 the designer this is what I get:

Why r u collapsed?

What am I missing here?

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...

Maurice · Accepted Answer · 2010-11-17T11:37:51.807

1

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());

edited Nov 17 '10 at 11:37

answered Nov 16 '10 at 07:51

Maurice

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Nope, I tried doing that, however, and still got the same result. What's the AB for? – Nov 16 '10 at 15:57
The ActivityBuilder creates the root element in the designer. Normally I use a WD.Load(path to XAML) and that works fine. But then I also use the Designer attribute to link Activity with ActivityDesigner. – Maurice Nov 16 '10 at 17:42
First, the Activity doesn't have a designer; its a compiled workflow. A workflow doesn't have a Designer attribute, but all the activities you drag into it do have them. I am loading and inspecting activities within an assembly, so I do not have the option of getting the original xaml. All I have are the workflow types and instances of those types. – Nov 16 '10 at 19:53
Thanks much for spending some time on this! This is the first time I've heard of that type, so I much appreciate your help on this. It does behave a little bit strangely, however. When I was testing it, I got a NRE in a call to CacheMetadata in one of my activities. But calling it again wouldn't result in an exception being thrown. I think the Workflow designer and runtime are a bit more careful with badly or hastily written activities. – Nov 17 '10 at 14:48

score 0 · Answer 2 · answered Nov 16 '10 at 21:00

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: the stream in Reflector

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.

The XAMl in the resources is actually slightly different that the XAML in the original file. The root element is no longer Activity but your DemoWorkflow. I have found another solution using the WorkflowInspectionServices, see my other message. — Maurice, Nov 17 '10 at 11:40
@maurice actually, the xaml in the resources is the serialized root workflow activity; its just that conceptually that root doesn't exist in your mental model of what you've designed. I've since seen you can configure deserialization to not throw when encountering protected/internal serialized properties. — , Nov 17 '10 at 14:52

Activities are always collapsed in rehosted designer

2 Answers2