ASP.NET server controls

The various types of ASP.NET server controls, which can be broken down into four broad categories:

·        Intrinsic controls -- these controls correspond to their HTML counterparts, or simulate one if none exists. Examples include the Button, ListBox, and TextBox controls.

·        Data-centric controls -- controls used for binding and displaying data from a data source, such as the DataGrid control.

·        Rich controls -- these controls have no direct HTML counterparts. Rich controls, like the Calendar control, are made up of multiple components, and the HTML generated will typically consist of numerous HTML tags (as well as client-side script), to render the control in the browser.

·        Validation controls -- like, for example, the RequiredFieldValidator, which can be used to ensure proper data input within a web form.

two additional types of controls that you should be aware of:

·        HTML Server Controls

·        User Controls

HTML server controls correspond directly to various HTML tags, and are defined within the System.Web.UI.HtmlControls namespace. These controls derive their functionality from the System.Web.UI.HtmlControls.HtmlControl base class. Microsoft provides this suite of HTML server controls for a couple of reasons:

·        Some web developers may prefer to work with the HTML-style of control that they're used to

·        Developers can convert existing HTML tags to HTML server controls fairly easily, and thus gain some server-side programmatic access to the control

The following HTML tag declaration is, believe it or not, a fully qualified HTML server control that can be accessed programmatically on the server within your web form's code:

<INPUT id="MyHTMLTextBox" type="text" name="MyHTMLTextBox"  
runat="server">

What makes this a programmable HTML server control? Simply the reference to runat="server. In this example, using runat="server" ensures that the .NET Framework will convert the HTML tag into a corresponding HtmlInputText object (there is an HTML server control object for every corresponding HTML tag). We also add id="MyHTMLTextBox", to provide a unique name of the object so that we can reference it in our server-side code