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ASP.NET Basics


ASP.NET is a server side technology for developing web based applications based on Microsoft .Net  Framework. ASP.NET is run on the web server. When a user click on a page/website link on a web browser, a request is sent to the web server. The web server reads the code and generates a web page . The web page is then sent to the browser where the client reads this page. Since the processing is on the server, it is called 'Server Side technology'.

Features of ASP.NET:
  1. It lets you write server side code using over 40 languages. Most popular being C# and VB
  2. ASP.NET pages are compiled, not interpreted
  3. It has full access to the functionality  of .Net Framework... XML, web services, database interaction, emails, regular expression
  4. You can separate server side code of your page from HTML layout
  5. Easy to reuse common User Interface elements

An ASP.NET page generally consists of the following:
1. Directive: Controls how page is compiles , how page is cached by web browser, error fixing, import classes. It start with <%@, followed by directive name, attribute,value and ends with %
example: 
<%@ Page Languauge = "VB" %> 
<% Import Namespace = "System.Web.Mail" %>
<% Register TagPrefix = "xx" TagName = "name", src = "footer.ascx">    // to register a user control
2. Code declaration block: Contains all application logic between <script>   </script> tags
eg: <script language = "VB" runat = "server">          
// code here
</script>
3. Code Render block: defines inline code or expression that will execute when page will render
<% Dim title as string = "example" %>
<%= title %>
4. ASP.NET server controls
5. Server Side comments. These are different from client side comments, as they do not get displayed in the client code
6. literal text and HTML tags

In short, ASP.NET pages are simply text files that have .aspx file extension. When a client requests a ASP.NET page, the web server passes the page to ASP.NET runtime. ASP.NET runtime reads the page and compiles it into .NET class. This class is then used to produce HTML that is sent back to the user. Each new request to the same page, need not go through all the steps and can respond directly.

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