Create an array of SqlParameter and pass it to SqlHelper.ExecuteDataset() .
SqlParameter[] paramArray = new SqlParameter[] {
new SqlParameter("@employeeId",Employeeid),
new SqlParameter("@firstname",Fname)
};
ds = SqlHelper.ExecuteDataset(con, CommandType.StoredProcedure, "GetemployeeId", paramArray);
P.S. This will only work if you have implemented ExecuteDataset to handle SqlParameter values being passed as an Array.