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Web Form Fundamentals
Chapter-2 Unit-2
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Problem with Response. Write
• Spaghetti code
When the individual output is to be modified the entire
code is to be revised
• Lack of flexibility
Modification of the page after a month, the entire
code needs to be read and later modified
• Confusing content and formatting
Difficulty in creating larger forms
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Problem with Response. Write
• Complexity
Tracking of different types of functionalities leads to complexity
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Server Controls
• ASP.NET provides two sets of Server Controls
HTML Server Controls• Contains equivalent HTML elements
• Use similar HTML tags
Web Controls• Similar to HTML controls
• Provide a richer object set
• Variety of properties and formatting
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Features of HTML control
• They generate their own interface
The properties are set and the underlying HTML tag is updated automatically when the page is rendered and sent to the client
• They retain their stateThe web pages can be created in the same way as
the windows page is created
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Features of HTML control
• They fire events
You can respond to these events just like ordinary controls in windows application
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The ViewState
• Traditional ASP
• A form is submitted to the server with the filled
information
• The Server returns back with error
• All the information's are lost when is page is viewed by
the user
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The ViewState
• The ASP.NET
• The form is submitted to the server with information
• The server returns the page back with error
• Now the page contains the information that was
given at the time the page was sent to the server
HOW? This is because ASP.NET maintains the
viewstate
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The ViewState
• The ViewState indicates the status of the page when
submitted to the server
• The Status is defined through the hidden field placed on each
page with a <form> tag, the hidden fields stores information
about the state
• Maintaining the ViewState is the default setting of the
ASP.NET
• If you do not want to maintain the ViewState include the
directive <%@Page EnableViewState=“false” %>
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The HTML control class
• The HTML server controls are available in the namespace
System.Web.UI.HtmlControls
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The HTML control class
Class Name Tag
HtmlAnchor <a>
HtmlButton <button>
HtmlForm <form>
HtmlImage <img>
HtmlInputButton <input type=“button”> <input type =“submit”>,<input type=“reset”>
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The HTML control class
HtmlInputCheckbox <input type=“checkbox”>
HtmlInputControl <input type=“text”>
HtmlInputFile <input type=“file”>
HtmlInputHidden <input type=“hidden”>
HtmlInputRadioButton <input type=“radio”>
HtmlSelect <input type=“select”>
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Events
• Web forms are event driven means every piece of code acts in response to the specific event
• The HtmlButtonClass provides the Server Click event
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Events
• Imports statement
It provides access to all the important namespace
• Custom Page class and control variables• Single event handler
This event handler retrieves the value from the textbox and converts it into the respected conversion
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Event handling changes
• Two parameters (source and e)• Recommended standard for .NET• It allows your code to identify the controls that
sent the event
Private sub convert_Serverclick(sender As Object,e as EventArgs)_Handles convert.ServerClick
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Event handling changes
• Second the event handler connects itself to
the appropriate event using the handles
clause
• AutoEventWireup is set to “false” so that the
ASP.NET will always rely on the Handles
keyword to connect to the event handlers<input type=“submit” value=“Ok” id=“convert” OnServerClick=“Convert_ServerClick”runat=“server”>
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HtmlControl Classes
• Every html control inherits from the base class HtmlControl
• HtmlControl Events– ServerClick - Click is processed on the server
side– ServerChange - This event reponds when a
change has been made to a text or selection control
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Events and Controls that provide it
Events Controls that provide itServerClick HtmlAnchor,Form,Button,
InputButton,InputImageServerChange Text,InputCheckBox,
RadioButton,Select
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HtmlInputImage control
• Click the image and the co-ordinates are to be displayed
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HtmlControlBase Class
• Each Html control inherits from the base class HtmlControl
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HtmlControl Base class
Property DescriptionAttributes Provides a collection of all tag attributes
and their valuesControl Provides the collection of control
available under current controlDisabled True Disables the control and the user
cannot interactEnableViewState True:It uses the hidden field to store the
information about the page
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HtmlControl Base class
Property DescriptionPage Provides a reference to the web page
that contains the controlStyle CSS style properties that can be used to
formatTag Name Indicates the name of the Html elementVisible False:The control is hidden from the user
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HtmlContainerControl class
• Any html control that requires a opening and closing tag also inherits from the HtmlContainer Control
• <a> - HtmlAnchor• <form> - HtmlForm• <div> - HtmlGeneric Control
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HtmlContainerControl class
Property Description
InnerHtml Html content between opening and closing of the tags,used for formatting<b>,<i>,<u>
Innertext The text content between the opening and closing of the tags
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HtmlInputControl class
Property Description
Type Provides the type of input control <input type=“submit”>
Value Returns the content of the control as string
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Page class
• Every web page is a custom class that inherits from the Page class
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Page Class Property
Fundamental Property DescriptionApplication & Session It holds the information
about the stateCache Stores Objects for reuseControls Provides a collection of
the web controls in that Page
EnableViewState
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Page Class Properties
Fundamental Property DescriptionIsPostBack Boolean Property checks
whether the Page is submitted for the first time
Request Refer to the HttpRequest object that holds the information about the current web request
Response Set the web response or redirect the user to other web page
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Page Class Properties
Fundamental Property Description
Server Refers to the HttpServer utility performs some tasks like URL,Html encoding
User If the user has been authenticated then this property will be initialized with the user information
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HttpRequest class
• The HttpRequest class encapsulates all the information related to the client request for a web page
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HttpRequest class
Property Description
ApplicationPath Gets the virtual directory (URL)PhysicalPath Gets the real directory (URL)
Browser Provides link to the HttpBrowserCapabilities object which contains the browser features
ClientCertificate Gets the security certificate if there exists one
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HttpRequest class
Property Description
Cookies Gets the collection cookies sent with the request
Headers\Servervariables
Provides a name\value collection of HTTP headers and server variables
IsAuthenticated IsSecureConnection
Returns true if user is authenticated and secure sockets are used
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HttpRequest class
Property Description
QueryString Provides the parameters that were passed along with query string
Url and UrlReferrer
Current address of the page and the address of the page from where the user has navigated from
UserAgent A string representing the browser type.IE provides the value “MSIE”
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HttpRequest class
Property Description
UserLanguages Provides a sorted string array that lists the clients language
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Server Variables
• Request Method• Server Name• Server Port• Server Protocol• Server Software
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The HttpResponse Class
• This class allows you to send information directly to the client
• Some of the important functionalities• Caching Support• Cookie features• Redirect method
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Property Description
BufferOutput Default set to (true) the page is not sent to the client
Cache Refers to the HttpCache policy
Cookies The collection of cookies sent with response
Write(),BinaryWrite()WriteFile()
Allows you to write text or binary content directly to the response stream
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Property Description
Redirect() Transfers the user to another page or another website
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The Server Utility Class
• The ServerUtility class provides some miscellaneous helper methods
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Property Description
CreateObject Creates an instance of the COM object that is identified by its ID
HtmlEncode,HtmlDecode
Changes an ordinary string into a string with legal HTML characters
UrlEncode,UrlDecode
Changes an ordinary string into a string with legal URL characters
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Property Description
MapPath Returns the Physical path
Transfer Similar to response.redirect method
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