<p>I am looking for any best practices or ideas on how you would create an interface with a DB from a .NET web application to upload data from Excel files
Should I use a mechanism that allows all the records to be loaded and flags the errors or should I use a mechanism that stops the load when an error occurs.</p>

<p>I've never had to deal with this type of requirement before so any help would be super!</p>

<p>Thanks</p>

do you want to put the excel files in the DB as a blob? or do you want to parse the files and put the records in the files into the db?
I'm assuming it is the latter.
As a user I'd like to have the option to know what the errors are so I can fix them and try again. I think how I try again depends on how much data I'm uploading.
I'd try to do a hybrid solution .. if there are only a few errors show a screen to correct those errors so the user can move on quickly. If there are a ton of errors you should just can it and have the user try all over again.
As far as the DB. Either have a separate table that uploads go into until they are checked and get with your "real" data, or have a UploadUniqueId column so you can roll-back any upload without much fuss.
delete tableName where UploadUniqueId = 'GUID'