How Do You Get a Power Page Attachment That’s Stored in Blob Storage

My Power App Portal (Power Pages) environments are configured to use Azure blob storage for form attachments. One of the primary reasons for doing this is to avoid filling up expensive dataverse storage with endless attachments submitted by enduers.

This article outlines how to set up Azure storage: link

What I’m going to demo is how to get ONE attachment that’s uploaded to a form. If your form allows multiple attachments, you’d simply loop through them.

In the example, I’m using the soon-to-be-obsolete dataverse connector, but the same basic flow design applies to the normal connector.

When a row is added to my table, the flow is triggered.
The flow then queries the Note (annotation) table using the ID from the source table.
filter query: (_objetid_value eq souce_table_id)

The list rows notes query will result in an array being returned, but I’m only dealing with one attachment, so there’s no need to loop through it. To avoid an unnecessary loop, a function can be used to target a single object from the array: first(body(‘List_rows_Notes’)?[‘value’])?[‘annotationid’]

From the Get row note action, annotationid and filename will be needed to help form the path to the blob. Using the concat function I’m combing the container name, annotationid, and filename. Also, note the transformation on annotationid, the hyphens need to be removed, and the string needs to be lowercase. The last part of the transformation is to remove .azure.txt from the filename.

concat('/blobcontainer/',toLower(replace(outputs('Get_row_Note')?['body/annotationid'], '-', '')),'/', split(outputs('Get_row_Note')?['body/filename'], '.azure.txt')[0])

The end result of the transformation will be:
/blobcontainer/annotationid/filename /blobcontainer/cf03e4cf7f72ad118561002248881923/example.pdf

With the path to the blob formed, the get blob content action can retrieve the file.

It’s that simple.

A couple of notes:
It would be wise to leverage a virus-scanning tool like Cloudmersive.
If you haven’t already noticed, when a user uploads a file that contains special characters in the name…it’s saved to the Note table without the special characters, but when it’s moved to blob storage, the characters will be in the name. Yes, that’s a bug Microsoft has yet to fix. You can avoid this by adding Javascript to the upload page to block files that fall into this category. OR. Write another flow to clean file names before the form is processed.
Uploaded filename: my report 1:2:3.pdf
Note table: my report 123.pdf
Blob: my report 1:2:3.pdf

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