The "spaghetti-code" problem described above with server controls is solved using ASP.NET.

Server controls are the tags that are understood by the server.

There are three kinds of server controls:

1. HTML Server Controls -This is the traditional HTML tags
2. Web Server Controls -This is the new ASP.NET tags
3. Validation Server Controls-This is used for input validation

HTML tags are the HTML server controls that are understood by the server.

In ASP.NET files,HTML elements are, by default, treated as text. Aadd a runat="server" attribute to the HTML element to make these elements programmable. This attribute indicates that the element should be treated as a server control and the id attribute is added to identify the server control.To manipulate the server control at run time, the id reference can be used.

Note: All HTML server controls must be present within a <form> tag with the runat="server" attribute. The runat="server" attribute indicates that the form should be processed on the server and it also indicates that the enclosed controls can be accessed by server scripts.

In the following example we declare an HtmlAnchor server control in an .aspx file and then we manipulate the HRef attribute of the HtmlAnchor control in an event handler (an event handler is a subroutine that executes code for a given event). The Page_Load event is one of the many events that ASP.NET understands:

The executable code itself has been moved outside to the HTML.

Web server controls are special ASP.NET tags that are understood by the server.

Like HTML server controls, Web server controls are also created on the server and they require a runat="server" attribute to work and also this controls do not necessarily map to any existing HTML elements and they may represent more complex elements.

The syntax for creating a Web server control is as follows:

In the following example we declare a Button server control in an .aspx file and then we create an event handler for the Click event which changes the text on the button:

To validate user-input,validation server controls is used.It will display an error message to the user,if the user-input does not pass validation.

Each validation control performs a specific type of validation (like validating against a range of valuesa or specific value).

By default, page validation is performed when a Button, ImageButton, or LinkButton control is clicked and you can prevent validation when a button control is clicked by setting the CausesValidation property to false.

The syntax for creating a Validation server control is: