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2.ASP.NET Server Controls - ASP.NET Web Forms
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2.ASP.NET Server Controls - ASP.NET Web Forms

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This is presentation about ASP.NET Server Controls, part of the free ASP.NET Web Forms Course in Telerik Academy. ...

This is presentation about ASP.NET Server Controls, part of the free ASP.NET Web Forms Course in Telerik Academy.
Telerik Software Academy: http://aspnetcourse.telerik.com
The website and all video materials are in Bulgarian

Table of contents:
Controls Class Hierarchy; HTML Server Controls; Web Server Controls; Web Server Control Life Cycle; HTML escaping; ASP.NET server controls; Example of ASP.NET server controls;

ASP.NET Web Forms Course @ Telerik Academy
http://aspnetcourse.telerik.com

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    2.ASP.NET Server Controls - ASP.NET Web Forms 2.ASP.NET Server Controls - ASP.NET Web Forms Presentation Transcript

    • ASP.NET Server Controls Web Controls. HTML Controls. HTML EscapingSvetlin NakovTechnical Trainerwww.nakov.comTelerik Software Academyacademy.telerik.com
    • Table of Contents1. Controls Class Hierarchy2. HTML Server Controls3. Web Server Controls  Basic Web Controls  Validation Controls  List Controls  Rich Controls4. Web Server Control Life Cycle5. HTML Escaping 2
    • What is ASP.NET Server Control? ASP.NET server controls  The smallest ASP.NET Component  Wrap an HTML UI element, or more complex UI  Component-oriented programming model  Executed and rendered at the server side Example of ASP.NET server controls:  <asp:Button>  <input type="submit">  <asp:Label>  <span>  <asp:GridView>  <table><tr><td>… 3
    • What is ASP.NET Server Control ?(2) Mandatory properties for all server controls:  runat="server"  ID="…" Programming model based on events  Each user interaction causes and event  Programmer decides which events to handle Browser-specific HTML is generated  Controls deliver appropriate HTML depending on browser type 4
    • Controls – Class Hierarchy
    • Controls – Class Hierarchy System.Web.UI.Control  Base for all controls  Properties – ID, Page, ViewState, Context, ClientID, Controls  Methods – Render(HtmlTextWriter writer) 6
    • Controls – Class Hierarchy (2) System.Web.UI.HtmlControls.HtmlControl 7
    • Controls – Class Hierarchy (3) System.Web.UI.WebControls.WebControl System.Web.UI.TemplateControl 8
    • HTML Server Controls
    • HTML Server Controls HTML server controls are very simple extension of Control class Look like traditional HTML  Defined by runat="server"  Simple HTML seems like text on the server  If an HTML element is converted to HTML server control, a server side object is associated with it Valid only inside a Web form tag: <form runat="server">…</form> 10
    • HTML Server Control – Example<%@ Page Language="C#" %><script language="c#" runat="server"> void ButtonSubmit_Click(Object sender, EventArgs e) { Response.Write("Value:<b>"+TextField.Value+"</b>"); }</script><html><head><title>HTML Server Controls</title></head><body> <form id="formMain" runat="server"> <input id="TextField" type="text" runat="server" /> <input id="ButtonSubmit" type="button" runat="server" value="Submit" onserverclick="ButtonSubmit_Click" /> </form></body></html> 11
    • HTML Server Controls Live Demo
    • HTML Server Control Classes HtmlForm – <form>…</form> HtmlInputText – <input type="text"> HtmlButton – <input type="button" /> HtmlAnchor – <a href="…">…</a> HtmlSelect – <input type="select"> HtmlTable, HtmlTableCell, HtmlTableRow – <table><tr><td>…</td></tr></table> HtmlImage – <img src="…" /> ... 13
    • HTML Server Control Classes (2) HtmlGenericControl  Used for all other HTML elements  <p>  <div>  <span>  <meta>  <body>  … 14
    • HtmlGenericControl – Example<%@ Page Language="C#" %><script runat="server"> void Page_Load(Object sender, EventArgs e) { this.MetaInfo.Attributes["name"] = "description"; this.MetaInfo.Attributes["content"] = "The page was generated on: " + DateTime.Now.ToString(); }</script><html><head> <meta id="MetaInfo" runat="server" /></head><body> <form id="formMain" runat="server">…</form></body></html> 15
    • HTML Generic Controls Live Demo
    • Web Server Controls
    • Web Server Controls Web server controls are server UI controls that abstract the common HTML elements  Have own lifecycle and functionality Come with .NET Framework  Located in System.Web.UI.WebControls namespace, inherit from the WebControl class HTML Abstraction Rendered HTML tags are quite different from the design-time markup 18
    • Web Server Controls – Features Rich functionality Type-safe programming capabilities Automatic Web browser detection AutoPostBack  Sumbit when the focus is lost Support for themes 19
    • Web Server Controls - Syntax tag_prefix Attributes are determines unique properties of the namespace for the Web control web control<tag_prefix:controlname attributes runat="server"/> Mandatory The name of attribute the control runat="server" 20
    • Web Server Control – Example<form id="formMain" runat="server"> <asp:Label ID="LabelResult" runat="server" Text="" Visible="false" /> <asp:TextBox ID="TextBoxInput" runat="server" /> <asp:Button ID="ButtonSubmit" runat="server" Text="Submit" OnClick="ButtonSubmit_Click" /></form>…protected void ButtonSubmit_Click( object sender, EventArgs e){ this.LabelResult.Text = "You entered: " + this.TextBoxInput.Text; this.LabelResult.Visible = true;} 21
    • Web Server Controls Live Demo
    • System.Web.UI. WebControls.WebControl The WebControl class defines properties, events and methods for all Web controls Control the appearance  BackColor  ForeColor  BorderWidth  BorderStyle  BorderColor 23
    • System.Web.UI. WebControls.WebControl (2) Control the behavior  Enabled  Visible  TabIndex  ToolTip … Not all controls support all these properties  See the documentation for details 24
    • Web Server Controls Basic Web Controls
    • Basic Web Controls  HTML<asp:button> <input type="submit"><asp:checkbox> <input type="checkbox"><asp:hyperlink> <a href="…"></a><asp:image> <img src="…"><asp:imagebutton> <input type="image"><asp:linkButton> <a href="…"></a><asp:label> <span>…</span><asp:listbox> <select size="5"></select><asp:panel> <div>…</div><asp:radiobutton> <input type="radio"><asp:table> <table>…</table><asp:textbox> <input type="text"> 26
    • Basic Web Controls: TextBox Creates single-lineor multiline text-box Lets the user to enter text Properties  Text  TextMode – SingleLine, MultiLine, Password  MaxLength  ReadOnly  AutoPostBack Events  TextChanged – combined with AutoPostBack 27
    • Basic Web Controls: Label Display static text in a <span> block Allows programmatically to manipulate it Properties CAUTION: the Text is NOT HTML encoded before it is displayed in the Label control.  Text This make it possible to embed script within HTML tags in the text.  AssociatedControlID – on click focus goes to the specified control Events  TextChanged – combined with AutoPostBack 28
    • Basic Web Controls: Literal Display static text Allows programmatically to manipulate it  Unlike the Label control, Literal does not let you apply styles to its content Properties CAUTION: the Text is NOT HTML encoded before it is displayed in the Literal  Text control. This make it possible to embed script within HTML tags in the text. Renders the Text property value directly 29
    • Basic Web Controls – Buttons Implement IButtonControl Properties  Text – buttons title  CommandName – pass a command  CommandArgument – pass command arguments  PostBackUrl – posts back to specified page  CausesValidation – perform validation or not  ValidationGroup – which validation group to be validated 30
    • Basic Web Controls – Buttons (2) Events  Click  Command  CommandName and CommandArgument are passed to code behind 31
    • Basic Web Controls – Buttons (3) Different button types  Button  Creates a push button  Submit button by default 32
    • Basic Web Controls – Buttons (4) Different button types  Command Button  Has command name associated (CommandName property)  Programmatically determine which button is clicked in Command event handles  Used in templated controls, e.g. GridView 33
    • Basic Web Controls – Buttons (5) Different button types  LinkButton  Same functionality as Button  Renders as hyperlink  Use Hyperlink if you want to link to another page  Renders JavaScript on the client browser 34
    • Basic Web Controls – Buttons (6) Different button types  ImageButton  Display an image that responds on mouse click  ImageURL – URL to displayed image  Both Click and Command events are raised 35
    • Buttons – Example<%@ Page Language="C#" AutoEventWireup="true"CodeFile="Buttons.aspx.cs" Inherits="Buttons" %><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head runat="server"> <title>Untitled Page</title></head><body> <form id="formMain" runat="server"> <asp:Button ID="ButtonEx" CommandName="ButtonEx" runat="server" OnClick="OnBtnClick" OnCommand="OnCommand" Text="Normal Button" /> <br /> 36
    • Buttons – Example (2) <asp:LinkButton ID="LinkButtonEx" runat="server" OnClick="OnBtnClick" Text="Link Button" CommandName="LinkButtonEx" OnCommand="OnCommand" /> <br /> <asp:ImageButton ID="ImageButtonEx" runat="server" CommandName="ImageButtonEx" ImageUrl="~/images/DotNet_Logo_Small.gif" OnCommand="OnCommand" OnClick="OnBtnClick" /> <br /> <asp:Label ID="LabelMessage" runat="server" Text=""></asp:Label> </form></body></html> 37
    • ButtonsLive Demo 38
    • Basic Web Controls – Panel The Panel control  Container for other controls  Rendered as <div> Useful for:  Displaying and hiding groups of controls  Generating and inserting controls at runtime 39
    • Basic Web Controls – Panel(2) Properties  ScrollBars – modify visibility and position of scroll bars  Wrap – value indicating whether the content wraps within the panel  GroupingText – caption for the group of controls that is contained in panel control  DefaultButton – button to be pressed by default (Enter) 40
    • PanelsLive Demo
    • Basic Web Controls – PlaceHolder The PlaceHolder control Reserves a space in the page control hierarchy  Used to add controls to the page at runtime  Does not produce any visible output Controls  Use it to add, insert or remove controls from PlaceHolder Control 42
    • Basic Web Controls – CheckBox Select between checked / unchecked Properties  Checked  Text – control caption  AutoPostBack  automatically posts back the page when control state is changed 43
    • Basic Web Controls – CheckBox (2)  CausesValidation – whether validation is performed  ValidationGroup – which validation group to be validated Events  CheckChanged 44
    • Basic Web Controls – RadioButton Creates a radio button on the Web Forms page Properties  Text  GroupName – allow a mutually exclusive selection from the group 45
    • Validation Controls Performing Control Validation
    • Validation Controls The ASP.NET Web forms validation controls  Validate the values that are entered into other controls of the page Two modes of validation  Client-side validation  Server-side validation Validation is performed at page submit 47
    • Validation Controls (2) Most important validation controls:  RequiredFieldValidator  RangeValidator  CompareValidator  RegularExpressionValidator  CustomValidator  ValidationSummary 48
    • Validation Controls Live Demo
    • List ControlsDisplaying Lists of Items
    • List Controls List Web controls  Display list of items, e.g. table of rows  Support binding to a collection  Display rows of data in templated format Expose DataSourceID, DataSource, DataMember properties Bind to collection that support IEnumerable, ICollection or IListSource 51
    • List Controls (2) ListBox CheckBoxList RadioButtonList Repeater DataList GridView DropDownList 52
    • List Controls Live Demo
    • Web Server Controls Rich Controls
    • Rich Controls Task-specific controls Built with multiple HTML elements Rich functionality Examples:  Calendar  AdRotator 55
    • Web ServerControls – Lifecycle
    • Phases Init ViewState Load Send Postback Change Notification Handle Postback events PreRender Save State Render Dispose Unload 57
    • Phases - Initialize Control initialize settings needed during incoming web request Init event (OnInit method) 58
    • Phases – Load View State At the end of this phase ViewState property is automatically populated Override LoadViewState method to customize state restoration LoadViewState method 59
    • Phases – Load Perform actions common to all requests Server controls in the tree are created and initialized Control state from previous round trip is restored including client – side data Load event (OnLoad method) 60
    • Phases – Send Postback Change Notification Raise change events in response to state changes between previous and current postbacks RaisePostDataChangedEvent method IPostBackDataHandler should be implemented 61
    • Phases – Handle Postback Events Handle client-side events caused postback Raise appropriate events on the server RaisePostBackEvent method IPostBackEventHandler should be implemented 62
    • Phases – PreRender Perform any updates before the control is rendered Changes made in this phase can be saved PreRender event (OnPreRender method) 63
    • Phases – Save State ViewState property is persisted Send to the client and back as a hidden field SaveViewState method 64
    • Phases – Render Generates the output which will be send to the client Any changes to controls state made here are lost Render() method 65
    • Phases – Dispose Final clean up Expensive resources should be released Dispose() method 66
    • Phases – Unload Final clean up Usually clean up is performed in previous phase so this event is not handled UnLoad event (OnUnLoad() method) 67
    • ControlsLifecycle Live Demo
    • HTML Escaping
    • What is HTML Escaping? HTML escaping is the act of replacing special characters with their HTML entities  Escaped characters are interpreted as character data instead of mark up Typical characters to escape  <, > – start / end of HTML tag  & – start of character entity reference  , " – text in single / double quotes … 70
    • Character Encoding Each character could be presented as HTML entity escaping sequence Numeric character references:  λ is &#955;, &#x03BB; or &#X03bb; Named HTML entities:  λ is &lambda;  < is &lt;  > is &gt;  & is &amp;  " (double quote) is &quot; 71
    • XSS Attack Cross-site scripting (XSS) is a common security vulnerability in Web applications  Web application is let to display a JavaScript code that is executed at the clients browser  Crackers could take control over sessions, cookies, passwords, and other private data How to prevent from XSS?  ALWAYS validate the user input  Perform HTML escaping when displaying text data in a Web control 72
    • What Offers ASP.NET? ValidateRequest attribute of Page directive  Checks all input data against a hard-coded list of potentially dangerous values  The default is true  Using it could harm the normal work on some applications  E.g. a user posts JavaScript code in a forum  Escaping is better way to handle the problem! 73
    • What Offers ASP.NET ? (2) HttpServerUtility.HtmlEncode  HTML encodes a string and returns the encoded string  Page.Server is instance of HttpServerUtility The following script <%response.write(Server.HTMLEncode("The image tag: <img>"))%> Output: The image tag: &lt;img&gt; Web browser renders the following: The image tag: <img> 74
    • HTML Escaping Live Demo
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