KB-1428 File Upload expression evaluation error within Interface Designer


Within the Interface Designer, when uploading a document to a File Upload field and selecting "Submit", the following error is displayed:

Could not display interface. Please check definition and inputs.
Interface Definition: Expression evaluation error at function a!fileUploadField [line X]: Error in a!forEach() expression during iteration 1: Expression evaluation error at function fn!content_appian_internal [line X]: Invalid Content ID

However, when navigating to the document folder, users see that the document uploaded correctly.


Files are moved from a temporary directory on upload to the final destination on submit. Once the file is moved to its destination, it gets a new ID and the ID associated with the file in the temporary directory is deleted. This error is expected in the Interface Designer because the new ID is unknown to the Interface Designer.


This is not a bug and is expected behavior for the Interface Designer. This is not an issue in Appian 17.4 because the behavior was changed to keep the file ID the same.

Affected Versions

This article applies to Appian 17.3 and below.

Last Reviewed: November 2017