topic Re: Expression of type: 'String' does not match the field: 'folderPath'. Expected type is 'object'. in Data Engineering

Expression of type: 'String' does not match the field: 'folderPath'. Expected type is 'object'.

Rutuja1997 — Thu, 22 May 2025 15:35:48 GMT

Hi Microsoft folks,

I am building a pipeline to copy the latest folder to the lakehouse from SFTP server.It could copy the folder when i entered the folder path manually but couldn't when I passed the folderpath dynamically using the concat function.Hardcoded path for example is '/Directory_name/folderName' .Now i want to dynamically pass the folderName from the the previous filter activity output which is filtering the latest folder.In the pipeline expression builder I wrote '

@concat('Directory_name/',activity('Filter1').output.Value[0].name).But getting "Expression of type: 'String' does not match the field: 'folderPath'. Expected type is 'object'." error.

I need this logic to build incremental pipeline to get the latest folder in the lakehous.

This is the filter activity payload {
"ItemsCount": 6,
"FilteredItemsCount": 1,
"Value": [
{
"name": "New_Extract_2*****64_1*************",
"type": "Folder"
}
]
}

Re: Expression of type: 'String' does not match the field: 'folderPath'. Expected type is 'object'.

nilendraFabric — Thu, 22 May 2025 21:51:52 GMT

Try this

{
"folderPath": "@concat('Directory_name/', activity('Filter1').output.Value[0].name)"
}

Re: Expression of type: 'String' does not match the field: 'folderPath'. Expected type is 'object'.

Rutuja1997 — Fri, 23 May 2025 07:08:18 GMT

Hi Nilendra, Thank you for replying promptly.I tried above suggestion it didn't work.It is showing

I tried this way as well didn't work

Re: Expression of type: 'String' does not match the field: 'folderPath'. Expected type is 'object'.

v-aatheeque — Mon, 26 May 2025 18:42:52 GMT

Hi Rutuja1997,
Based on the error " Double quoted string is not allowed"
Expression of type: 'String' does not match the field: 'folderPath'. Expected type is 'object.

can you try the below path :

{ "folderPath": @concat('Directory_name/', activity('Filter1').output.Value[0].name) }

If this post was helpful, please consider marking Accept as solution to assist other members in finding it more easily.

Re: Expression of type: 'String' does not match the field: 'folderPath'. Expected type is 'object'.

v-aatheeque — Thu, 29 May 2025 17:27:36 GMT

Hi Rutuja1997,

we haven't heard back from you regarding our last response and wanted to check if your issue has been resolved.

If the response addressed by the community member for your query, please mark it as Accept Answer and click Yes if you found it helpful.

Thank You.

Re: Expression of type: 'String' does not match the field: 'folderPath'. Expected type is 'object'.

v-aatheeque — Mon, 02 Jun 2025 06:49:58 GMT

Hi Rutuja1997 ,

If the information is helpful, please accept the answer by clicking the "Upvote" and "Accept Answer" on the post. If you are still facing any issue, please let us know in the comments. We are glad to help you.

We value your feedback, and it will help us to assist others who might have a similar query. Thank you for your contribution in enhancing Microsoft Fabric Community Forum.

Re: Expression of type: 'String' does not match the field: 'folderPath'. Expected type is 'object'.

v-aatheeque — Thu, 05 Jun 2025 17:55:39 GMT

Hi Rutuja1997 ,

Just checking in regarding the issue you reported with the error "Double quoted string is not allowed" and the mismatched field type for 'folderPath'. As suggested earlier,

If this resolves your problem, kindly mark the answer as Accepted to help others in the community. If you're still encountering issues, feel free to update the thread we're here to help!

Thank you for contributing to the Microsoft Fabric Community.

Re: Expression of type: 'String' does not match the field: 'folderPath'. Expected type is 'object'.

Rutuja1997 — Thu, 12 Jun 2025 16:38:15 GMT

Hi Fabric Community,

Apologies for late feedback.The issue was solved by using set variable activity.I stored the concatenated string in set variable and passed that in the folder path.That way i could solve that problem.

Re: Expression of type: 'String' does not match the field: 'folderPath'. Expected type is 'object'.

Vaughan_Brant — Mon, 15 Jun 2026 10:58:13 GMT

Doesn't work when referencing Variable Library values either. Despite the warning messages the pipeline will save and copy activity does work. It is however, disconcerting that the copy activity shows these errors.

If I use a Set Variable activity and concat the two values and use that in the copy activity. I don't see the error.

In the Set Variable activity:

@concat(pipeline().libraryVariables.Files_Temp_Path, '/', pipeline().libraryVariables.Files_Temp_Filename)

and in the Copy Data activity:

@variables('FilePath')