If you are just talking about 'using Excel data' from c#, you have a number of options
1) export the data from excel as csv/tsv to a file and read that file in c# : easy
2) use Excel Interop from C# : Way more complex - see this for a start (but you'll need to do a lot more research' likely)
http://www.dotnetperls.com/excel[
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3) I believe you can use ADO.NET to read data from an Excel spreadsheet - you'll need to Google for 'how to set it up'
4) There may be 3rd party solutions free or not that can read Excel Spreadsheets
obviously the choice on 1,2,3,4 depends on many things, none of which we can ascertain on the information you've provided