I can't figure out why some activities in the WF designer do not expand.
Looking at the sample documentation for the WizardActivityPack activities:
But when I try to open the same file in Visual Studio 2010's WF designer:
If I look at the file using the XML editor I can see all the activities are in the file, but the designer only shows me the one box and I cannot click into or expand it.
You have to place the *.design.dll somewhere that visual studio can find it. Like in the %programfiles(x86)%\Microsoft Visual Studio 10.0\Common7\IDE\PublicAssemblies.
VS looks for designers by convention; if the activities are in an assembly called Activity.dll, VS looks for its design classes in an assembly called Activity.Design.dll under VS' codebase (and subdirectories) or (I believe) in the GAC.
This fact is important to know when creating your own activities/designers! The reason behind this is so that your Activity assembly doesn't need to reference the Designers dll; you can deliver the Activity assembly by itself to production while leaving the Designers dll on the design machine.
(If you reference the *.Design.dll from your Activities assembly, or if they exist in the same assembly, this doesn't apply. The recommended pattern is to separate the two and allow VS to load them via convention. For an example of this, see this sample.)
add this line new DesignerMetadata().Register(); to WPF presentation
来源：https://stackoverflow.com/questions/8886238/vs-workflow-designer-not-expanding-activities