Dynamic parameters in user activity?

Question

We are reinstalling WF-4 in our application. We have something called a filter. Now we need activity to run this filter and work with the results in ForEach. Simple enough. But these filters have a list of parameters (to start the filter) that need to be filled in on the workflow node. The list of filter parameters can be anything from 0 to N.

After the user sets FilterId, is there a way to create an instance of this filter, view its list of parameters and add these parameters to the Activity? Parameters are basically just Name, Type and need its value populated by the user.

Another thing, we do not want to instantiate the filter at runtime, which would be too expensive. At run time, we just need a filter identifier and a list of parameter values.

I would be happy to have a static property for the parameters if there is a way to update it when FilterId modifies and checks that all the parameters in this list have values.

Answer 1

I didn’t do it myself, but if I’m not mistaken, I saw other people doing something similar by implementing the ICustomTypeDescriptor interface. And this is what Interop activity uses to display WF3 activity properties as WF4 InArgument / OutArguments.