Please correct me if I am wrong.
In Windows workflow once you create a sequence or flowchart diagram, you can add the service reference to the project and trigger the workflow. (I managed to do).
but lets say in the middle of the workflow user input is needed to continue then how it can be done? I saw few sample like the "Number guessing" sample from Microsoft still not clear.
and
Whats the purpose of WorkFlowInvoker
?
This isn't a trivial topic and you certainly need todo a bit more research on the subject. Start by looking at 'Pick' activities. link