The Application object can store information that persists for the entire lifetime of an application (a group of pages with a common root). Generally, this is the whole time that the IIS server is running. This makes it a great place to store information that has to exist for more than one user (such as a page counter). The downside of this is that since this object isn't created anew for each user, errors that may not show up when the code is called once may show up when it is called 10,000 times in a row. In addition, because the Application object is shared by all the users, threading can be a nightmare to implement. You can use the Application object to share information among all users of a given application. An ASP-based application is defined as all the .asp files in a virtual directory and its subdirectories. Because the Application object can be shared by more than one user, there are Lock and Unlock methods to ensure that multiple users do not try to alter a property simultaneously.

With Response.Outout.Write options are available to you to write the formatted out put.

Init() - when the page is instantiated. Load() - when the page is loaded into server memory. PreRender() - the brief moment before the page is displayed to the user as HTML. Unload() - when page finishes loading.

Web forms are very similar to traditional HTML forms. The difference is that Web forms are server-based, meaning you create the user elements on the server. The server has complete knowledge of what the interface looks like, what it can do what data it expects, and so on. Web forms pages are divided into two parts: the visual elements and the accompanying UI logic. These two components are completely separate from each other conceptually, and they can be physically located anywhere you want. Typically, both parts are contained within one .aspx file. The System.Web.UI namescape defines classes and interfaces used in constructing nd rendering elements on a Web form. The most important class in the System.Web.UI is the Control class which defines the properties, methods and events that are common in all server controls in the WebForm framework. Another important class in this namespace is Page which is a derivative of the Control Class. All ASP.NET web pages are instances of derivatives of the Page Class. To have an extensible framework, the System.Web.UI namespace also includes the UserControl class which is similar to Page class except that it is mainly used as the base class for user controls.

HTML Server controls: HTML elements are completely client-based; the server has no knowledge of any of these controls. A browser knows what <input type="text"> is supposed to look like and renders it accordingly. HTML server controls are server-side elements. They're objects that are created on the server, with properties, methods, and events that you can handle. They generate HTML for the browser to display. HTML server controls are very easy to create-simply add the runat="server" attribute to any HTML element. Every HTML element has a corresponding HTML server control. <input type="text" id="MyTextBox" runat="server" /> Once you turn an HTML element into an HTML server control, every attribute of the element can be modified through code. Web controls: Web server controls are similar to HTML server controls. They're created on the server and allow you to build complex user interfaces easily. They require the runat="server" attributes to work correctly. They also provide rich programmatic capabilities. Unlike HTML server controls, however, Web controls don't necessarily map one-to-one to HTML elements and can represent more complex UI elements.

A struct is a value type while a class is a reference type. There's no inheritance with struct.