asp.net mvc transactionscope class

i want to add transactionscope class in 开发者_运维知识库vs 2010. where can i find it? in which namespace. according to msdn there is a system.transaction but there is not? is it extenal?

You need to add reference to the System.Transactions.dll assembly in your project and the TransactionScope class is located in the System.Transactions namespace.