Using Excel interop is a bad idea as it isn't supported and it's going to fail and give you all sorts of errors. Also no doubt you're still coding this on your local development machine and haven't tried to deploy it yet so have no idea the issues you face.
Instead use a library that is designed to do this from asp.net. google "open source library reading excel asp.net" and you'll find some likely candidates;
c# - Import and Export Excel - What is the best library? - Stack Overflow[
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You can use the Open XML SDK or the Excel ODBC driver, but there are lots of third party libraries out there too.