Why don't you use SSIS (SQL Server Integration Services) to import the data into your database ? That is the fastest way to do it. If you want to do it using asp.net you can use the OleDbConnection to access the Excel sheet.
OleDbConnection oconn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + Server.MapPath("example.xls") + ";Extended Properties=Excel 8.0");
You can access the data by specifying the sheet name.
OleDbCommand ocmd = new OleDbCommand("select * from [Sheet1$]", oconn);