Slide 12.1: Web forms

Web Forms

All server controls must appear within a <form> tag, and the <form> tag must contain the runat="server" attribute. The runat="server" attribute indicates that the form should be processed on the server.

It also indicates that the enclosed controls can be accessed by server scripts. The form is always submitted to the page itself.

 <form runat="server">

   ...HTML + server controls

 </form>

If you specify an action attribute, it is ignored. If you omit the method attribute, it will be set to method="post" by default.

REQUEST_METHOD: GET
The input values from the form are sent as part of the URL, and saved in the Request.QueryString collection. For example, after submit the keywords: ASP.NET and form to the Yahoo, the URL is changed to:
```
   http://search.yahoo.com/search?p=ASP.NET+form
```
The value of the Request.QueryString["p"] is “ASP.NET form” if Yahoo uses the ASP.NET. The code ‘+’ is for the space ‘ ’ in the URL.

REQUEST_METHOD: POST
Data is sent as a standard input stream to the program. For ASP.NET, the data is usually retrieved from objects such as TextBox.

An .aspx page can only contain ONE <form runat="server"> control! Also, if you select view source in an .aspx page containing a form with no name, method, action, or id attribute specified, you will see that ASP.NET has added these attributes to the form:

 <form name="_ctl0" method="post" action="page.aspx" id="_ctl0">

    ...some code

 </form>