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ASP.Net Basics

ASP.Net Basics. Course Textbook: Build Your Own ASP.Net Website: Chapter 2. Lesson Objectives. Introduces more advanced ASP.Net topics such as: ASP.Net Page Structure ASP.Net Server Controls Directives View State Namespaces. ASP.Net Page Structure.

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ASP.Net Basics

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  1. ASP.Net Basics Course Textbook:Build Your Own ASP.Net Website: Chapter 2

  2. Lesson Objectives • Introduces more advanced ASP.Net topics such as: • ASP.Net Page Structure • ASP.Net Server Controls • Directives • View State • Namespaces

  3. ASP.Net Page Structure • An ASP.Net page consists of the following elements: • Directives • Code declaration blocks • Code render blocks • ASP.Net server controls • Server-side comments • Server-side include directives • Literal text and HTML tags • Not every element always appears on a given page, we will learn when to use them

  4. Directives • Control how the page is compiled • Specify settings when transferring between pages • Aid in debugging • Allow importing of classes • Start with the <@ sequence and end with a %> sequence • ASP.Net directives can appear anywhere on the page, but are usually placed as the first lines in the file

  5. Three Common Directives • The Page directive defines page-specific attributes like the language to be used as in: • <%@ Page Language=“C#” %> • The Import directive makes functionality defined elsewhere through the use of namespaces as in: • <%@ Import Namespace=“System.Web.Mail” %> • The Register directive links a user control to the ASP.Net page as in: • <%@ Register TagPrefix=“ux” TagName=“footer” Src=“footer.ascx” %>

  6. Code Declaration Blocks • When you add programming logic to your .aspx page, it resides inside a <script runat=“server”> tag • Code declaration tags usually are placed in the <head> of your ASP.Net page • If you don’t specify the language of the code, it will default to the language in the Page directive • <script runat=“server” language=“C#”>

  7. Code Render Blocks • Used to define inline code or inline expressions • <% String Title = “Harry Potter”; %> • <% Title %> • The first line contains a complete line of C# code, the declaration and assignment of a String variable • The second line writes out the Title variable onto the page

  8. ASP.Net Server Controls • Server Controls represent the dynamic elements users interact with. • There are four types of server controls: • HTML Controls • ASP.Net Controls • Validation Controls • User Controls • Most server controls must reside within a <form runat=“server> tag

  9. Advantages of Server Controls • HTML elements can be accessed from within code to change their characteristics, check their values, or dynamically update them • ASP.Net controls retain their properties even after the page was processed. This process is called the View State • With ASP.Net controls, developers can separate the presentational elements and the application logic so they can be considered separately

  10. What is the View State??? • The persistence of data after it is sent to the server for processing is possible because of the View State • If you have created forms using HTML controls, you have experienced the loss of data after form submission • The data is maintained in the view state by encrypting it within a hidden form field

  11. ing at the View State • Look at the source code of the file after the page has been submitted to see code similar to this… • i.e. <input type= hidden” name=“VIEWSTATE” value=“dWtMTcy0TAy0DawNzt)PDtsPGk6Mj47PjtsPHQ802w8aTWzPj+02wPGw5uAXJdGFaGaxk6t4=“ /> • The View State is enabled for every page by default • If you don’t intend to use the View State, set the EnableViewState property of the Page directive to be false • <%@ Page EnableViewState=“False” %>

  12. Server-Side Comments • Server-side comments will not be processed by ASP.Net • It used the <%-- beginning sequence and the --%> ending sequence • <% -- This is a server-side comment --%> • The difference between HTML comments and ASP.Net comments is that ASP.Net comments are processed by the browser or the ASP.Net runtime • Don’t use HTML comments to comment out ASP.Net code • HTML comments only hide things from the browser

  13. Server-Side Include Directives • These includes help developers insert segments of code into a page from an external file • There are two techniques for doing this: • Using the file attribute, we give the physical path to the file on the server either as an absolute path starting from the drive letter or a relative path to the current file • <! -- include file=“myinclude.aspx” --> (relative path) • Using the virtual attribute, you can specify the file’s location from the absolute root of the site, or from a relative path to the current page. • <! -- include virtual=“/directory1/myinclude.aspx” --> (absolute path

  14. Literal Text and HTML Tags • One cannot do without text and HTML elements to display information from your ASP.Net controls and programming code • Without these there would be no format to the page • The surrounding <html>, <head>, and <body> tags make it possible for a browser to understand our page

  15. Languages • .Net supports many different languages • Programmers used to VBScript or JavaScript to do their programming will have more robust, strongly-typed, and feature-rich choices in VB.Net and C#.Net • VB.Net builds on the RAD that became popular in the 90’s. VB.Net is easy to read, use and maintain. • C#.Net was developed to keep the simplicity of VB and the power and flexibility of C++ (some say to replace Java). C# does away with confusing C++ syntax.

  16. Summary • On an ASP.Net page, you will probably use: directives, code declaration blocks, code render blocks, includes, comments, and controls. • Two languages supported by ASP.Net are VB.Net and C#.Net. We will focus on C#.Net syntax for this course. • In the next chapter we will cover some C# programming basics.

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