Programming Microsoft ASP.NET 4 - Dino Esposito [446]
the Scripts and Services collections on the ScriptManager and ScriptManagerProxy controls are merged at run time.
Note
The ScriptManagerProxy class is a simple wrapper around the GetCurrent method of the ScriptManager class, and its programming interface is not an exact clone of the ScriptManager. From within the proxy, you have access only to a limited number of properties, including Scripts, Services, AuthenticationService, RoleService, and ProfileService. If you need to modify anything else, refer to the GetCurrent static method of the ScriptManager class.
Script Binding and Loading
By extensively relying on client capabilities, an Ajax page requires a lot of script code. The framework itself links a lot of code, as do custom controls and actual user pages. The only HTML-supported way of linking script files is the