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ASP.net(1.1)原理学习笔记--第二章 web Form 网页视窗

2005-08-06 09:47 661 查看
一，服务器端控件ASP.NET使用服务器端控件，建立WEB Form模型。在传统的html元素中添加一个属性runat = server，就能创建一个服务器端控件，并且会自动在Page派生类中创建一个字段，以该元素名为字段名，以该元素的类型为控件类型。如此一来，该.aspx页面就和桌面控件类似，用同一个页面就能处理和客户的交互与响应。相反，在传统的asp中，需要额外的编程。二，使用隐藏字段_VIEWSTATE.net使用名为_VIEWSTATE的hidden控件来保存网页的所有状态，可用来保存控件的先前值。Listing 2-3 Accumulator Page
<!— Accumulator.aspx —>
<%@ Page Language="C#" %>

<html>
<script runat=server>
protected void Page_Load(object src, EventArgs e)
{
if (IsPostBack)
{
int op1 = int.Parse(_op.Value);
int op2 = int.Parse(_sum.InnerText);
_sum.InnerText = (op1+op2).ToString();
}
}
</script>
<body>
<form runat=server>
<h2>ASP.NET accumulator page</h2>
<input size=2 type=text id=_op runat=server/>
Sum:<span id=_sum runat=server>0</span>
<p>
<input type=submit value="Add" />
</p>
</form>
</body>
Listing 2-4 Accumulator Page Rendering
<html>

<body>
<form name="_ctl0" method="post"
action="accumulator.aspx" id="_ctl0">
<input type="hidden" name="__VIEWSTATE"
value="dDwtMTE3NzEwNDc2Njs7PvcRil1nMNe70yha9afq+YEvj46N" />

<h2>ASP.NET accumulator page</h2>
<input name="_op" id="_op" type="text" size="2" />
Sum:<span id="_sum"></span>
<p>
<input type=submit value="Add" />
</p>
</form>
</body>

</html>

三，事件
标准CLR服务器端事件机制:委托。
1，显式自动绑定委托订阅事件:一般服务器端控件都提供一个EventHandler委托(DataGridItemEventHandler使用DataGridItemEventArgs)
Listing 2-5 Server-Side Event Handler Using Explicit Delegate Subscription
<!— event.aspx —>
<%@ Page Language="C#" %>

<html>
<script runat=server>
protected void OnClickMyButton(object src, EventArgs e)//显式创建EventHandler的新实例，并用OnClickMyButton函数初始化该实例ServerClick
_message.InnerText = "You clicked the button!";
}

protected void Page_Init(object src, EventArgs e)//利用了Page_Init自动事件绑定技术
{
_MyButton.ServerClick +=
new EventHandler(OnClickMyButton);//委托订阅_MyButton的ServerClick事件
</script>
<body>
<form runat=server>

<h2>ASP.NET event page</h2>
<p>
<input type=button id=_MyButton
value="Click me!" runat=server />
</p>
<span id=_message runat=server/>
</form>
</body>
</html>
２，使用OnEvent语法来绑定事件：
Listing 2-6 Server-Side Event Handler Using OnEvent Syntax
<!— event.aspx —>
<%@ Page Language="C#" %>

<html>
<script runat=server>
protected void OnClickMyButton(object src, EventArgs e)
{
_message.InnerText = "You clicked the button!";
}
</script>
<body>
<form runat=server>
<h2>ASP.NET event page</h2>
<p>
<input type=button id=_MyButton
value="Click me!"
OnServerClick="OnClickMyButton" runat=server />
</p>
<span id=_message runat=server/>
</form>
</body>
</html>
四，使用两个隐藏字段来控制回送的控件，__EVENTTARGET产生回送的控件的标志符, __EVENTARGUMENT传递事件的参数,
Listing 2-7 Color Page Demonstrating Three Separate Server-Side Event HandlersListing 2-7 Color Page Demonstrating Three Separate Server-Side Event Handlers
<!— color.aspx —><%@ Page Language="C#" %><html><script runat=server>protected void OnRed(object src, EventArgs e){_color.Style["background-color"] = "Red";}protected void OnGreen(object src, EventArgs e){_color.Style["background-color"] = "Green";}protected void OnBlue(object src, EventArgs e){_color.Style["background-color"] = "Blue";}protected void Page_Init(object src, EventArgs e){_redButton.ServerClick   += new EventHandler(OnRed);_greenButton.ServerClick += new EventHandler(OnGreen);_blueButton.ServerClick  += new EventHandler(OnBlue);}protected void Page_Load(object src, EventArgs e){if (!IsPostBack){_color.Style["background-color"] = "Red";_color.Style["width"] = "100";_color.Style["height"] = "100";}}</script><body><form runat=server><h2>ASP.NET color page</h2><div id=_color runat=server /><p><input type=button id=_redButton value="Red"runat=server /><input type=button id=_greenButton value="Green"runat=server /><input type=button id=_blueButton value="Blue"runat=server /></p></form></body></html>
Listing 2-8 Color Page Rendering
<html><body><form name="_ctl0" method="post"action="color.aspx" id="_ctl0"><input type="hidden" name="__EVENTTARGET" value="" /><input type="hidden" name="__EVENTARGUMENT" value="" /><input type="hidden" name="__VIEWSTATE" value="dD...==" /><script language="javascript"><!—function __doPostBack(eventTarget, eventArgument) {var theform = document._ctl0;theform.__EVENTTARGET.value = eventTarget;theform.__EVENTARGUMENT.value = eventArgument;theform.submit();}// —></script><h2>ASP.NET color page</h2><div id="_color"style="background-color:Red;width:100;height:100;"/><p><input language="javascript"onclick="__doPostBack('_redButton','')"name="_redButton" id="_redButton"type="button" value="Red" /><input language="javascript"onclick="__doPostBack('_greenButton','')"name="_greenButton" id="_greenButton"type="button" value="Green" /><input language="javascript"onclick="__doPostBack('_blueButton','')"name="_blueButton" id="_blueButton"type="button" value="Blue" /></p></form></body></html>
五，web页面的生命周期
Figure 2-5. Page Event Sequence
六，使用Code-Behind技术来写Web Form代码
Listing 2-10 Sample Page with Server-Side Controls and Code-Behind
<!— WebFormPage2.aspx —><%@ Page Language="C#"Inherits="EssentialAspDotNet.WebForms.Page2"Src="Page2.cs" AutoEventWireUp="false" %><html><body><form runat=server><h3>Enter name:<input type=text id=_name runat=server/></h3><h3>Personality:<select id=_personality runat=server /></h3><input type=button id=_enterButtonvalue="Enter" runat=server/><p runat=server id=_messageParagraph /></form></body></html>
Listing 2-11 Code-Behind File for Sample Page
// Page2.csusing System;using System.Web;using System.Web.UI;using System.Web.UI.HtmlControls;using System.Web.UI.WebControls;namespace EssentialAspDotNet.WebForms{public class Page2 : Page{protected HtmlSelect         _personality;protected HtmlInputText      _name;protected HtmlInputButton    _enterButton;protected HtmlGenericControl _messageParagraph;override protected void OnInit(EventArgs e){// Wire up handler to ServerClick event of button_enterButton.ServerClick += new EventHandler(OnEnter);}override protected void OnLoad(EventArgs e){// On initial access, populate select with itemsif (!IsPostBack){_personality.Items.Add(new ListItem("extraverted"));_personality.Items.Add(new ListItem("introverted"));_personality.Items.Add(new ListItem("in-between"));}}protected void OnEnter(object src, EventArgs e){// When the user presses enter, print a messagestring msg = string.Format("Hi {0}, you selected {1}",_name.Value, _personality.Value);_messageParagraph.InnerText = msg;}}采用了字段绑定技术
Figure 2-6. Binding Fields to Server-Side Controls七，如果要在服务器端控件中引用根目录，可以使用 "~"，它被解释成对Request.ApplicationPath的引用。Listing 2-12 Using Root Path Reference Syntax
<!— RootPathSyntax.aspx —><html><body><h1>Root path reference test page</h1><form runat="server"><a href="~/otherpages/hi.aspx" runat="server"><img runat="server" src="~/images/hi.gif"/></a></form></body> </html>八，HtmlControl控件都是从System.Web.UI.Control，尤其是System.Web.UI.HtmlControls.HtmlControl基类派生。
Figure 2-7. HtmlControl HierarchyTable 2-1. Tag Mappings for HtmlControls
TagHtmlControl Class
<img runat=server/>HtmlImage
<input type=file runat=server/>HtmlInputFile
<input type=hidden runat=server/>HtmlInputHidden
<input type=image runat=server/>HtmlInputImage
<input type=radio runat=server/>HtmlInputRadioButton
<input type=text runat=server/>HtmlInputText
<input type=checkbox runat=server/>HtmlInputCheckBox
<form runat=server>HtmlForm
<span runat=server><div runat=server><p runat=server> etc. (all other elements)HtmlGenericControl
<select runat=server/>HtmlSelect
<table runat=server/>HtmlTable
<td> (within a server-side table)<th> (within a server-side table)HtmlTableCell
<tr> (within a server-side table)HtmlTableRow
<textarea runat=server/>HtmlTextArea
<a runat=server/>HtmlAnchor
<input type=button runat=server />HtmlInputButton
<input type=submit runat=server />HtmlInputButton
<input type=reset runat=server />HtmlInputButton
九，WebControl控件
Figure 2-8. WebControl Hierarchy列表控件：Listing 2-13 ListControl Properties
public class ListControl : WebControl{public virtual bool     AutoPostBack          {get; set;}public virtual string   DataMember            {get; set;}public virtual object   DataSource            {get; set;}public virtual string   DataTextField         {get; set;}public virtual string   DataTextFormatString  {get; set;}public virtual string   DataValueField        {get; set;}public virtual ListItemCollection Items       {get; set;}public virtual int      SelectedIndex         {get; set;}public virtual ListItem SelectedItem          {get;}public event EventHandler SelectedIndexChanged;//...}
Figure 2-9. Rendering of CheckBoxList and RadioButtonList ControlsListing 2-14 Sample Use of Xml, AdRotator, and Panel Controls
<!— File: XmlAdPanel.aspx —><%@ Page language="c#" %><HTML><body><form runat="server"><asp:Xml id=_xml1 runat="server"DocumentSource="sample.xml"TransformSource="sampleTransform.xsl"></asp:Xml><br/><asp:AdRotator id=_ar1 runat="server"Width="468px" Height="60px"AdvertisementFile="pics.xml"></asp:AdRotator><asp:Panel id=_p1 runat=server HorizontalAlign='center'Visible='true' bgColor='cornsilk'><asp:Label id=_l1 runat=server>Panel label</asp:Label><br/><asp:TextBox id=_tb1 runat=server/><br/><asp:Button Text='Push me!' runat=server/></asp:Panel></FORM></body></HTML>
十，Web控件和Html控件的区别
Web控件的层次与处理都比较简单
Html控件对asp和html页面的升级到.net比较方便十一，VS.net处理WebForm十二，小结AsP．NET用webForm将基于控件的编程方法引入web应用程序开发。借鉴于熟悉的桌面应用程序控件模型，  ASP．NET定义了许多控件类，用于表示Web窗体上的元素。这些控件把它们自己生成为HTML，作为对HTTP请求的响应的一部分。在服务器上对这些控件所做的任何更改，以后都会在客户生成方面反映出来，从而让开发者更专注于应用程序的构造，而不必花费太多的精力于浏览器生成方面的细节。为了使这种基于控件的编程模型能用于网页上的所有元素．AsP．NET引入了viewstate，作为一种转换控件状态(该状态不能作为标准PosT请求的一部分来传送)的手段。服务器端事件完善了控件模型。可以使用两套服务器端控件类：Htmlcontrol控件类和Webcontrol控件类。Htmlcontrol类严格地反映了它们对等的HTML标记，能方便地将现有的HTML网页转换为ASP.NET。而Webcontrol类提供了一种更加统一的编程接口，大多数开发者在从头开始构建 asp.net网页时，都会选择使用它。

                                            

                                        

                        
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