What is controller layer and where we put this in our 3-tier architecture?1)UI2)Business Logic Layer3)Data Access LayerI search in net but unable to get exact ans.Any links or sample example helps to understand better.Thanks. 
Controller layer and 3-tier architecture
architecture;asp.net
The controller layer is at the UI. It is basically controlling what action should take place in your application. Since you tagged this with asp.net, you should consider looking at Microsoft's version of this structure (called MVC for Model, View, Controller) - ASP.NET MVCEdit: Seeing your comment, I've never attempted to shoe-horn MVC into the old WebForms way of life, but it looks like others have - codeproject