Build Your Own ASP.NET 2.0 Web Site Using C# & VB, Second Edition

all the code inside the .aspx file instead), the Page class is still used—we just

don’t see it.

We can use a range of user interface elements inside the form—including typical,

static HTML code—but we can also use elements whose values or properties can

be generated or manipulated on the server either when the page first loads, or

when the form is submitted. These elements—which, in ASP.NET parlance, are

called controls—allow us to reuse common functionality, such as the page header,

a calendar, a shopping cart summary, or a “Today’s Quote” box, for example,

across multiple web forms. There are several types of controls in ASP.NET:

❑

HTML server controls

❑

web server controls

❑

web user controls

❑

master pages

There are significant technical differences between these types of controls, but

what makes them similar is the ease with which we can integrate and reuse them

in our web sites. Let’s take a look at them one by one.

HTML Server Controls

HTML server controls are outwardly identical to plain old HTML tags, but include

a runat="server" attribute. This gives the ASP.NET runtime control over the

HTML server controls, allowing us to access them programatically. For example,

if we have an <a> tag in a page and we want to be able to change the address to

which it links dynamically, using VB or C# code, we use the runat="server"

attribute.

A server-side HTML server control exists for each of HTML’s most common

elements. Creating HTML server controls is easy: we simply stick a runat="serv-

er" attribute on the end of a normal HTML tag to create the HTML control

version of that tag. The complete list of current HTML control classes and their

associated tags is given in Table 4.1.

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HTML Server Controls

Table 4.1. HTML control classes

Associated TagsClass

<a runat="server">HtmlAnchor

<button runat="server">HtmlButton

<form runat="server">HtmlForm

<img runat="server">HtmlImage

<input type="submit" runat="server">HtmlInputButton

<input type="reset" runat="server">

<input type="button" runat="server">

<input type="checkbox" runat="server">HtmlInputCheckBox

<input type="file" runat="server">HtmlInputFile

<input type="hidden" runat="server">HtmlInputHidden

<input type="image" runat="server">HtmlInputImage

<input type="radio" runat="server">HtmlInputRadioButton

<input type="text" runat="server">HtmlInputText

<input type="password" runat="server">

<select runat="server">HtmlSelect

<table runat="server">HtmlTable

<tr runat="server">HtmlTableRow

<td runat="server">HtmlTableCell

<th runat="server">

<textarea runat="server">HtmlTextArea

<span runat="server">HtmlGenericControl

<div runat="server">

All other HTML tags

For more details on these classes, see Appendix A.

All the HTML server control classes are contained within the System.Web.UI.Htm-

lControls namespace. As they’re processed on the server side by the ASP.NET

runtime, we can access their properties through code elsewhere in the page. If

you’re familiar with JavaScript, HTML, and CSS, then you’ll know that manipu-

lating text within HTML tags, or even manipulating inline styles within an HTML

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Chapter 4: Constructing ASP.NET Web Pages