Excel Column Validator is a reusable OutSystems extension designed to validate the structure of uploaded Excel (.xlsx) files before any data processing begins.

The component reads the header row of the first worksheet and compares it against a JSON array of expected column names provided as input. This ensures that uploaded Excel files match the required schema and prevents runtime errors caused by missing or incorrectly named columns.

The action accepts the Excel file as BinaryData and a JSON array of expected column names as input parameters. It returns a comma-separated list of missing columns if any expected columns are not found. If validation fails due to an invalid file, corrupted Excel document, missing worksheet, or invalid JSON format, an appropriate error message is returned.

Column comparison is case-insensitive and automatically trims leading and trailing whitespace to avoid mismatches caused by formatting differences. The component validates only the first worksheet and only the first row, which is treated as the header row.

The implementation uses Microsoft’s DocumentFormat.OpenXml library, making it enterprise-safe and free from commercial licensing restrictions. This makes the component suitable for production environments where licensing compliance is critical.

Excel Column Validator is ideal for scenarios such as bulk data imports, template enforcement, master data onboarding, regulatory submissions, financial uploads, HR data ingestion, and administrative portals where maintaining strict Excel template structure is essential for data integrity and system reliability.