For using a .NET custom library (DLL) in a Workflow, you have to:

  1. copy DLL into WorkflowEditor and WorkflowServer folder, e.g. MyLibrary.dll.
  2. Start Workflow Editor and open your Workflow Template which should use the DLL
  3. Click on the "Add assembly reference..." item

  4. Which will show a file open dialog (filtered to *.dll") and located to the directory where the WFEditor runs. You can select a DLL to add.
  5. *.DLL file selection is only accepted if it is located in the Workflow Editor directory otherwise an error message will appear.
  6. When a valid DLL has been selected the XAML is modified
  7. Reload the Workflow Template