From C#, you use ADO.NET, connect to the database that contains the data and query it. There is nothing to it, and it is not related to VFP.
A SQL Server database is a repository of data. Which client you use to access that data is immaterial to SQL Server. So it is perfectly OK to insert data from a VFP front-end and retrieve it from C# as you want to do.
If you are unfamiliar with C# and ADO.NET, there are forums here for them where you can ask about the SQLServer OleDB provider in .NET