Read PDF with OCR doesn't work with C# projects

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1

Hi,

I am not able to use the activity Read PDF with OCR. I have the following message error:
A warning message states that multiple languages requiring compilation, specifically C#, are detected in the activity definition and advises converting all expression activities to a single language. (Captioned by AI)

I am using Studio 2024.10.8 with C# language (Windows project) and the package UiPath.PDF.Activities 3.16.0. For the rest of the packages, I am using the latest versions.

I tried to isolate the activity in a workflow as described in the 2.8 section of this topic Troubleshooting Guide : Conversion from Windows-Legacy project to Windows project but I still have the message error.

Do you have any idea of how to make this activity work in a C# Project?

Thanks a lot for your help!

3

@melanie

Try to change the system packages and pdf package versions and check if the issue persists

Cheers

4

The issue occurs because Read PDF with OCR internally uses VB.NET expressions, while your project is in C#. Since Windows projects enforce a single-language rule, this causes a compilation conflict.

  1. Use an Isolated Workflow (Ensure Arguments are Correct)

You mentioned trying this, but double-check these steps:

  1. Create a Separate Workflow (.xaml)
    Right-click your project → Add → Sequence(or a new workflow).
    Ensure this new workflow is VB.NET-based (not C#).
    Move the Read PDF with OCR activity into this workflow.

  2. Pass Arguments Properly
    Define In/Out arguments to send/receive data between your C# main workflow and the VB.NET workflow.

  3. Convert Project to VB.NET

If your project isn’t deeply reliant on C#, consider converting it back to VB.NET(though not ideal if you prefer C#).

5

I can confirm this behaviour, the activity seems broken in a C# project. This can be demonstrated by opening a fresh C# project and trying to add the activity, no OCR engines can be added to it whereas in a VB.NET project you can.

I suggest you raise a bug report via the UiPath Helpdesk.
I’ll try to mention it to the product managers and also point out the documentation here contains a project that is in legacy format and should be updated.

1 Like
6

Can you please try to update to at least 3.19.1 and see if it still reproduces?

We have fixed an issue that seems like yours in that particular patch https://docs.uipath.com/activities/other/latest/document-understanding/release-notes-uipath-pdf-activities#v3191

7

It does appear that the result from Ioana may fix your immediate issue, however there is still the issue where new PDF OCR activities cannot be added in a C# project (and I think it might be related), so that is also reported as a bug now.

Hope the documentation in the above release notes does fix your issue though!

Edit, seems to be some nuance here related to the OCR engine activities being in a different package and them not being so intuitive to find, but thats not related to the language issue and more a case of if anyone reads this in the future, its perhaps not a bug that the C# project doesn’t get the OCR engines but that the Ux isn’t as straightforward as maybe it could be.

2 Likes
8

Hi,

I am not able to update the package UiPath.PDF.Activities. The latest available on my side is 3.16.0.

Thanks

9

Hi,

Thanks a lot for your help!

I am not sure I have understood the end of your message, I also opened a ticket to UiPath on my side and I hope they’ll fix it soon :crossed_fingers:

Best regards,