c# barcode generator code 39 Internet Visitor Using Web Browser 1 7 in C#.NET

Encoding Code 39 in C#.NET Internet Visitor Using Web Browser 1 7

Internet Visitor Using Web Browser 1 7
Code 3 Of 9 Generation In Visual C#.NET
Using Barcode maker for VS .NET Control to generate, create Code 39 Extended image in .NET framework applications.
www.OnBarcode.com
Recognize ANSI/AIM Code 39 In Visual C#.NET
Using Barcode decoder for Visual Studio .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
Internet Three Tier Web Application Hosted on Web Server 2
Printing European Article Number 13 In Visual C#.NET
Using Barcode generator for Visual Studio .NET Control to generate, create EAN13 image in .NET framework applications.
www.OnBarcode.com
Barcode Printer In C#
Using Barcode maker for Visual Studio .NET Control to generate, create Barcode image in .NET framework applications.
www.OnBarcode.com
Presentation Tier
Generating ECC200 In C#
Using Barcode printer for Visual Studio .NET Control to generate, create DataMatrix image in .NET framework applications.
www.OnBarcode.com
QR Code 2d Barcode Printer In Visual C#.NET
Using Barcode generation for Visual Studio .NET Control to generate, create QR Code ISO/IEC18004 image in VS .NET applications.
www.OnBarcode.com
Business Tier
USS Code 128 Printer In C#.NET
Using Barcode encoder for Visual Studio .NET Control to generate, create Code-128 image in .NET framework applications.
www.OnBarcode.com
Leitcode Maker In Visual C#
Using Barcode creator for .NET Control to generate, create Leitcode image in VS .NET applications.
www.OnBarcode.com
Data Tier
Paint Code 3 Of 9 In Java
Using Barcode encoder for Java Control to generate, create Code-39 image in Java applications.
www.OnBarcode.com
USS Code 39 Creator In None
Using Barcode generation for Software Control to generate, create USS Code 39 image in Software applications.
www.OnBarcode.com
Figure 2-2. Internet visitor interacting with a three-tier application
Creating UPC Symbol In VS .NET
Using Barcode printer for Reporting Service Control to generate, create UPC-A image in Reporting Service applications.
www.OnBarcode.com
Drawing DataMatrix In Objective-C
Using Barcode printer for iPad Control to generate, create Data Matrix 2d barcode image in iPad applications.
www.OnBarcode.com
CHAPTER 2 LAYING OUT THE FOUNDATIONS
Barcode Printer In .NET
Using Barcode generation for ASP.NET Control to generate, create Barcode image in ASP.NET applications.
www.OnBarcode.com
Encode Data Matrix ECC200 In Objective-C
Using Barcode creation for iPhone Control to generate, create Data Matrix ECC200 image in iPhone applications.
www.OnBarcode.com
Finally, the presentation tier generates an updated view of the shopping cart (step 6). The results of the execution are wrapped up by generating an HTML (Hypertext Markup Language) web page that is returned to the visitor (step 7), where the updated shopping cart can be seen in the visitor s web browser. Note that in this simple example, the business tier doesn t do a lot of processing, and its business logic isn t very complex. However, if new business rules appear for your application, you would change the business tier. If, for example, the business logic specified that a product could only be added to the shopping cart if its quantity in stock was greater than zero, an additional data tier call would have been made to determine the quantity. The data tier would only be requested to update the shopping cart if products are in stock. In any case, the presentation tier is informed about the status and provides human-readable feedback to the visitor.
Quick Response Code Generation In None
Using Barcode generation for Font Control to generate, create QR Code ISO/IEC18004 image in Font applications.
www.OnBarcode.com
Code 128 Code Set A Maker In Objective-C
Using Barcode encoder for iPad Control to generate, create Code 128C image in iPad applications.
www.OnBarcode.com
What's in a Number
Encode Code39 In None
Using Barcode drawer for Font Control to generate, create Code39 image in Font applications.
www.OnBarcode.com
Barcode Decoder In Visual C#.NET
Using Barcode reader for .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
It s interesting to note how each tier interprets the same piece of information differently. For the data tier, the numbers and information it stores have no significance because this tier is an engine that saves, manages, and retrieves numbers, strings, or other data types not product quantities or product names. In the context of the previous example, a product quantity of 0 represents a simple, plain number without any meaning to the data tier (it is simply 0, a 32-bit integer). The data gains significance when the business tier reads it. When the business tier asks the data tier for a product quantity and gets a 0 result, this is interpreted by the business tier as Hey, no products in stock! This data is finally wrapped in a nice, visual form by the presentation tier, such as a label reading, Sorry, at the moment the product cannot be ordered. Even if it s unlikely that you want to forbid a customer from adding a product to the shopping cart if the product is not in stock, the example (described in Figure 2-3) is good enough to present in yet another way how each of the three tiers has a different purpose.
Painting Barcode In Visual Studio .NET
Using Barcode maker for Reporting Service Control to generate, create Barcode image in Reporting Service applications.
www.OnBarcode.com
Code 39 Full ASCII Maker In Objective-C
Using Barcode maker for iPad Control to generate, create Code 39 Extended image in iPad applications.
www.OnBarcode.com
User clicks on Add to Cart button.
User is informed that the product can't be added to the shopping cart.
Presentation Tier
Add this product to shopping cart. The product is unavailable.
How many units do we have in stock
Business Tier
Data Tier
Figure 2-3. Internet visitor interacting with a three-tier application
CHAPTER 2 LAYING OUT THE FOUNDATIONS
The Right Logic for the Right Tier
Because each layer contains its own logic, sometimes it can be tricky to decide where exactly to draw the line between the tiers. In the previous scenario, instead of reading the product s quantity in the business tier and deciding whether the product is available based on that number (resulting in two data tier, and implicitly, database, calls), you could have a single data tier method named add_product_if_available that adds the product to the shopping cart only if it s available in stock. In this scenario, some logic is transferred from the business tier to the data tier. In many other circumstances, you might have the option to place some logic in one tier or another or maybe in both. In most cases, there is no single best way to implement the three-tier architecture, and you ll need to make a compromise or a choice based on personal preference or external constraints. Furthermore, there are occasions in which even though you know the right way (in respect to the architecture) to implement something, you might choose to break the rules to get a performance gain. As a general rule, if performance can be improved this way, it is okay to break the strict limits between tiers just a little bit (for example, add some of the business rules to the data tier or vice versa), if these rules are not likely to change in time. Otherwise, keeping all the business rules in the middle tier is preferable because it generates a cleaner application that is easier to maintain. Finally, don t be tempted to access the data tier directly from the presentation tier. This is a common mistake that is the shortest path to a complicated, hard-to-maintain, and inflexible system. In many data access tutorials or introductory materials, you ll be shown how to perform simple database operations using a simple user interface application. In these kinds of programs, all the logic is probably written in a short, single file, instead of separate tiers. Although the materials might be very good, keep in mind that most of these texts are meant to teach you how to do different individual tasks (for example, access a database), and not how to correctly create a flexible and scalable application.
Copyright © OnBarcode.com . All rights reserved.