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Condition - Attachment Contains Causes Error

We have an alerting system that sends out messages, however the status of the alert (success/failure) is contained within a .txt attachment on the email. I am attempting to create a flow that will send me a notification based on the presence of the word "failed" in the text of the attachment.


I created the following flow based on the post here: Save attachment based on content

with the exact condition of: @contains(base64ToString(items('Apply_to_each')?['ContentBytes']), 'failed')

This results in the following error:


InvalidTemplate. Unable to process template language expressions for action 'Condition at line '1' and column '2394: 'The template language function baseo4ToString expects its parameter to be a string. The provided value is of type 'Null'. Please see for usage details.'.


Removing the conversion from base64tostring only causes the error to change to the following:


InvalidTemplate. Unable to process template language expressions for action 'Condition at line '1' and column '2394' : 'The template language function 'contains' expects its first argument 'collection' to be a dictionary (object), an array or a string. The provided value is of type 'Null'.'.


Based on this, I believe I am incorrectly requesting the attachment contents from Flow. The attachment I am testing with is a basic ASCII text file with no special characters or affectations created on a Windows PC using VSCode. I do not believe there is anything unique about the text file I am using to cause this behavior.


What error am I making in the way I am fetching the content of the email attachment?

Community Support Team
Community Support Team

Re: Condition - Attachment Contains Causes Error

Hi @AaronDubin,


Could you please share a screenshot of your flow's configuration?


I have made a test on my side and don't have the issue that you mentioned. My flow's configuration as below:

  • Add a "When a new email arrives" trigger, Has Attachment field and Include Attachments field are both set to Yes.
  • Add a "Apply to each" action, input parameter set to Attachments dynamic content of the trigger.
  • Within "Apply to each", add a Condition, click "Edit in advanced mode", type the following formula:
@contains(base64ToString(items('Apply_to_each')?['ContentBytes']), 'failed')

     Within "If/yes" branch of Condition, add a "Send me an email notification" action.


Image reference:25.JPG

The flow works successfully as below:26.JPG



Please check if you have set Has Attachment field and Include Attachments field to Yes within the "When a new email arrives" trigger on your side.


Best regards,


Community Support Team _ Kris Dai
If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

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