Transaction in asp.net

Hi all,
i am working on developing a  distributed web application and i am using ASP.net(C#) , sql server 2008 db, so in my senerio a customer can add multiple orders at once if any one order  could not inserted than all records must b rollback i did this logic through tranasction but still i am confuse if customers are more than one and they are going to add multiple records at the same time than deadlock occurs so how can i do this .
my code is follows
System.Data.SqlClient.SqlTransaction st = DAL.DataAccessLayer.SqlHelper.GetTransaction("order");
// here begin transaction               
                    DataTable dt = (DataTable)ViewState["Order"];
                    ...