u can read data from excel sheet in the same way u do from database. Only the connection string will change depending on microsoft office version.
Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\MyExcel.xls;Extended Properties="Excel 8.0;HDR=Yes;IMEX=1";
If it dont work, u can search others from: http://www.connectionstrings.com/excel
Then for data access query, thhe table name will be the sheet name with '$' sign appended. For eg, suppose sheet name is "Sheet1", query will be:
select * from [Sheet1$]
U can read data by using your data access method (e.g. OledbConnection and OledbCommand) into DataTable. After that, using ur method, u can insert into sql server database.