Book VI 1 in Visual C#

Encoding USS Code 39 in Visual C# Book VI 1

Looking at How ASPNET Works with C#

ASP NET Web Application Presentation Layer (Web Form ) Business Logic Generated NET Code Persistent Library

ASPNET is a library of controls and processing logic that makes constructing the server side of things much easier You construct server pages, but they end up transformed into the documents that the client uses to show you the user interface ASPNET is classified as a Web Application Framework, not a programming language The programming language, for our purposes, is C# However, you can code for ASPNET in any NET language it is just another set of tools in the framework C# is the language that you use to tell the server how to organize the ASP NET pieces and send them to the client The clients will never see any C# code; they won t even know that you coded it in C#

This gets into the same discussion that we have several times throughout the book regarding the difference between the library and the language ASP NET is a library of tools, and that library is language independent You orchestrate the functionality of the parts of the library using the language There are a few little caveats to Web development, however The client which doesn t care a whit that you are coding in C# needs some care and feeding There is no state in Web applications, so you need to think a little differently The client does a lot automatically for you in Web development The server has some security concerns Before we dig into the details of using C# with ASPNET, I d like to take a tour through the details of Web development and point out some things you need to keep in mind So here we go

When you are writing a Windows Form, WPF, or console application, your platform for the client is a Windows computer When you are writing a Web application, you have no idea what the platform for your client is It could be a Mac, any one of 12 Windows operating systems, or Linux It could be a phone, a tablet, or a netbook It could be a television, a gaming device, or a refrigerator (really: see Figure 1-3)

The point is that you don t know what you are writing for, so you have a very different development experience for a Web browser than you do for a Windows client You don t know what size the screen is, you don t know what language the machine is set to, you don t know how fast the connection to the Internet is You know nothing about your client

You have to question the client You can t assume much about the browser, so you have to make certain design decisions differently than you usually would You can depend on the browser to do some things for you that you might be used to having to do for yourself The programming details are explained in 4, but it is important to get a good overview now First, the client browser has a built-in scripting system called ECMAScript Second, the browser can tell you some subset of details about itself, its host machine, and the user that is using it

By now you get the idea that communication with the browser occurs via the network, and that the client and browser are disconnected Although that is true, the client isn t completely out in the fog when it comes to interacting with the user You can send a script along with your HTML document This script references objects on the screen just like your C# code would and makes things happen for the user Usually this script is in the JavaScript language Why not C# Well, C# isn t a scripting language C# needs to be compiled, and JavaScript isn t compiled It just sits there, in text, waiting for the browser to run it The fact that it is in text means you have to be careful not to put secure information in a script Right-click on any Web page in your browser and click View Source to see that page s script code A lot of the script that your pages need will be generated by ASPNET This book is about C#, not JavaScript, so we focus on the server features, not the client features For now, you should just know that things are happening on the client side, however