I’m new to ELSA Workflows. I have followed the guidance here to build an ELSA server, and the guidance here to build an ELSA Studio. Both worked fine and I can run both, and use the designer to create and execute flows.

Then I added a custom activity as described here to my ELSA server project. This new activity then appeared in the designer. However, when I try to add this custom activity to a flow, the designer shows the following error:

JsonException: The JSON value could not be converted to Elsa.Api.Client.Shared.Models.WrappedInput. Path: $ | LineNumber: 0 | BytePositionInLine: 10.

Reloading my flow definition (in the designer) shows an empty flow. Any attempt to add any activity to it then gives this error:

ArgumentException: An item with the same key has already been added. Key: name (Parameter ‘propertyName’)

I am using Elsa v3.1.3 NuGet packages.

The guidance page for custom activities does talk about using custom activities in the designer, with steps to put the custom activity code into the designer project. But this doesn’t make sense to me. Why does the designer need to know the full code for the activity (including how to execute it)? And why does the designer display my custom activity (only defined in the ELSA server project) in the toolbox, but then not let me add it?

I was expecting that the custom activity (defined in the ELSA server project) would be visible in the ELSA Studio toolbox (which it is) and that I could then drag it onto the design surface to add to a flow definition.