.net项目的代码结构指南

I generally use IoC pattern in my projects which are most of the time ASP.net based. Are there any guidelines on how to structure the projects in a general 3 layered project UI+BL+Data Access. I want to know more about how the folders should be created, where should constants be kept at within each layer (I keep all the strings such as query string parameters, stored procedure parameter etc in file named Constants which is singleton). How should I create classes that interact with Data Access layer from Business Layer etc. and all such code structure questions. I generally use IoC pattern in my projects whic