asp.net中的高性能数据库访问层

I am developing a applicatin which are having more than 5000 users once upon time. I using ASP.NET 3.5 framework for developement. I want to develope a high performance DAL Layer using latest technolgies like linq,ADO.NET Entity,ADO.NET Data services. I also want to make sure that it shuld be generic to all the future developement. Can any one pleasae Let me know which pattern i should use to develope that Database Access Layer. I am also want to use microsoft enterprise library for that.I am developing a applicatin which are having m