SQL-Backed Excel Diff App

I need a small web application that sits on IIS and talks to a SQL Server database. Its job is straightforward: every day one “master” Excel file lands in a network folder, while another file—same structure—can arrive several times a day. The app should watch that folder, pull in any new spreadsheets automatically, drop their contents into SQL, and then generate a comparison report based on date and site name. Report on rows in each file that are not found in the other. There is a field in both sheets that links the records.

Key behaviours I must see
• Automated folder monitoring is the only import path I need; no manual upload screen is necessary.
• When the multi-import file contains rows we already hold, the system should keep the first version and quietly ignore the duplicates.
• The detailed report has to be easy to read on the web page and exportable to Excel or CSV for further analysis. It should spell out what changed, by column, plus show new and missing rows.

Deliverables
• IIS-ready ASP.NET (Core or Framework) application, source code included.
• Normalised SQL Server schema and any required stored procedures or ETL scripts.
• Configuration file or admin screen for setting the watch folder path and scheduled scan interval.
• Deployment and setup guide so I can reproduce your environment on our test server.

Once the core workflow is proven, I’m open to light UI polish, logging, or scheduled email of the report, but the essentials above come first.