Methods to enable Sql Notification Services

What is the difference in the follow开发者_如何学Cing mentioned things, are these used for differnet purposes or are they used collectively for some functionality, can anyone please differentiante among these based on their functionalities:

   1) SqlCacheDependencyAdmin.EnableNotifications(ConnStr)
   2) AspNet_RegSql.exe -S "ServerName" -d "DatabaseName" -ed
   3) set enable_broker
   4) SqlDependency.Start(connStr)