Design considerations in Visual C#

Creation Code39 in Visual C# Design considerations

The principle design consideration for accessibility is to use the features Set the alternate text Use the tab indexing Set a default focus Make your application easy to use for everyone There is a new feature in Visual Studio 2010 called Check Page for Accessibility, which checks WCAG and Section 508 errors If you use this feature, warnings will actually be posted to your build process

Have you ever been to a site with a three-part US phone number shown as three textboxes You can usually automatically tab between them, and this structure makes sure you have exactly the right number of digits in each text box That s something that you might very well use on every page of many applications, right That phone number control consists of things that we already have around us: text box controls, client-side scripting, and validation All that you need is to put them together

The technology that you use to combine existing controls in useful ways is called a User Control, or ASCX ASCX is encapsulated, easy to create, and easier to use

To show you what I mean, here I show you how to make my favorite user control, the Phone Number control In this incarnation, it is only good for US format, but that s okay It gets the point across Just follow these steps to create a phone number control:

2 Select Web User Control (See Figure 3-9)

6 Right-click the designer and select View Code 7 Add a property to the code-behind that allows a page using the control to get to the phone number The goal is to get all the content from the controls, patch it together, format it, and deliver it as a public property Here is the code:

private string _phoneNumber; public string PhoneNumberValue { get { _phoneNumber = stringFormat( ({0}){1}-{2} ); return _phoneNumber; } }

So now we have a control just like the controls in the Toolbox that accepts a phone number in pieces and formats it nicely Let s play with it

You ll love using this control It really does work just like a Toolbox control Follow these steps to see how it works:

2 Change to the design view 3 Drag the ascx control right from the Solution Explorer onto the design

surface Ta da! The control shows up just like a plain text box would, but it is just like we formatted it Check out Figure 3-10

Add some code to populate the label on the button click, like this:

using using using using using using System; SystemCollectionsGeneric; SystemLinq; SystemWeb; SystemWebUI; SystemWebUIWebControls;

namespace _3 { public partial class UseThePhoneNumber : SystemWebUIPage { protected void Button1_Click(object sender, EventArgs e) { Label1Text = PhoneNumber1PhoneNumberValue; } } }

6 Right-click on the ASPX page and set it as the start page 7 Press <F5> and run the application Enter a phone number in the control and click the button The formatted phone number should appear in the label This is a boring example, but you can see how this can be used to collect commonly used fields together for reuse in an application Order details, addresses, and map coordinates, among other types of information, all are usually grouped together and make great user controls In a travel application I recently worked on, the start city and date and the end city and date became user controls It s a great way to solve simple reuse problems

Beyond the scope of a user control is a control that perhaps no one has thought of before Maybe your company makes a device with a pressure gauge that you need to replicate in code Or perhaps you need to display a unique set of patient statistics on a monitor, or demonstrate the running of some data engine Those kinds of controls call for the next level: custom controls, sometimes called server controls A custom control is a Web control built using essentially the same tools that Microsoft used to build the controls that we have used throughout this chapter I won t fool you building a server control is nontrivial To get one started, you need a whole new project, not just a new file The project type is a Server Control project, and it gives us a whole battery of code to start with, much like this: