Logic App Standard error calling Transform using Data Mapper XSLT action: undefined. undefined

I have been testing Data Mapper for almost maybe 4 months since the first private previews. Still, I have usually tried the Data Mapper capabilities and not the interaction between Logic Apps Standard workflow and the Data Mapper. Now that I’m preparing and finalizing my session for the Azure Logic Apps Community Day 2023, I’m finding these little headaches in trying to put these pieces working together. You also need to be aware that this behavior and experience may change in the future since DaTa Mapper is still in preview.

So, while I was trying to call a transformation created by the new Data Mapper, in this case, a JSON to JSON transformation, running locally in my machine, I was always getting this really annoying and non-sense error since it doesn’t provide any real and valuable help or insight on the issue we are facing:

  • undefined. undefined

Sometimes I think the Microsoft developer team likes that I write all these Errors and Warnings, Causes and Solutions blog posts, or they are just teasing us.

I was surprised to see this error since I just finished developing my map, and I had successfully tested it on the Data Mapper editor.


The reason for this error to happen is that I forgot to read the prerequisites for this preview extension which are well explained here: Announcement: Azure Logic Apps’ New Data Mapper for Visual Studio Code (Preview).

And that you can see in action in this video of Kent Weare:


For the map to run successfully in runtime, within your local.settings.json file in your logic apps standard project, ensure you have the following property configuration:

  • FUNCTIONS_WORKER_RUNTIME property set to dotnet-isolated.
  • And add the AzureWebJobsFeatureFlags property with the value: EnableMultiLanguageWorker

As you can see in the sample below:

  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated",
    "AzureWebJobsFeatureFlags": "EnableMultiLanguageWorker",

Hope you find this helpful! So, if you liked the content or found it helpful and want to help me write more content, you can buy (or help buy) my son a Star Wars Lego! 

Author: Sandro Pereira

Sandro Pereira lives in Portugal and works as a consultant at DevScope. In the past years, he has been working on implementing Integration scenarios both on-premises and cloud for various clients, each with different scenarios from a technical point of view, size, and criticality, using Microsoft Azure, Microsoft BizTalk Server and different technologies like AS2, EDI, RosettaNet, SAP, TIBCO etc. He is a regular blogger, international speaker, and technical reviewer of several BizTalk books all focused on Integration. He is also the author of the book “BizTalk Mapping Patterns & Best Practices”. He has been awarded MVP since 2011 for his contributions to the integration community.

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