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Expressions works in Condition, not as trigger

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Posted on 7 Jul 2022 06:55:51 by Stefanovic83

Hi All,

I'm trying to define a trigger condition, to make the flow run only when the filename contains the string "Uren". The expression I wrote works as a Condition Action, but returns and error when set as trigger condition. If I understand the error correctly, it's trying to read the filename before it's present in the flow, returning a null. How can I fix this?

Expressions: contains( base64ToString(triggerOutputs()?['headers/x-ms-file-name-encoded']),'Uren')

Error: InvalidTemplate. Unable to process template language expressions for trigger 'When_a_file_is_created_or_modified_in_a_folder' at line '1' and column '16216': 'The template language function 'base64ToString' expects its parameter to be a string. The provided value is of type 'Null'. Please see https://aka.ms/logicexpressions#base64ToString for usage details.'.

The flow:

flow with error.jpg

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Stefanovic83 22 on 22 Jul 2022 at 10:05:57

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Re: Expressions works in Condition, not as trigger

So is the logic then like this?

When "Uren.xlsx is modified, the condition trigger returns 'Uren'.
When something else is modified, the conditrion trigger returns null

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v-bofeng-msft on 22 Jul 2022 at 01:49:14

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Re: Expressions works in Condition, not as trigger

Hi @Stefanovic83 ,

Cause null value causes an error (base64ToString cannot handle null values), So I add conditional statements to circumvent triggerOutputs()? ['headers/x-ms-file-name-encoded']) If it is empty, it will be no error.

Best Regards,

Bof

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Stefanovic83 22 on 21 Jul 2022 at 18:12:39

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Re: Expressions works in Condition, not as trigger

Yeah that works @Shuvam-rpa . I just don't understand yet why. Could you explain?

The only difference is you adding that first part of the statement:

@if(empty(triggerOutputs()?['headers/x-ms-file-name-encoded']),false,contains( base64ToString(triggerOutputs()?['headers/x-ms-file-name-encoded']),'Uren'))

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v-bofeng-msft on 12 Jul 2022 at 06:32:22

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Re: Expressions works in Condition, not as trigger

Hi @Stefanovic83 ,

Please try:

@if(empty(triggerOutputs()?['headers/x-ms-file-name-encoded']),false,contains( base64ToString(triggerOutputs()?['headers/x-ms-file-name-encoded']),'Uren'))

Best Regards,

Bof

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Stefanovic83 22 on 07 Jul 2022 at 15:38:52

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Re: Expressions works in Condition, not as trigger

Thanks @Shuvam-rpa but my question was for the expression for the trigger condition.
I got already the flow working using an action Condition. 🙂

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Shuvam-rpa 891 Super User 2024 Season 1 on 07 Jul 2022 at 07:38:59

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Re: Expressions works in Condition, not as trigger

@Stefanovic83 kindly use below expression
contains(triggerOutputs()?['headers']?['x-ms-file-name'],'Uren')

please check below screenshot for reference

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