http://www.cnblogs.com/Clingingboy/archive/2006/09/29/514722.html????? 上一篇討論了為服務(wù)器控件添加客戶(hù)端功能,這一篇我們所要講的是控件生成器


1.錯(cuò)誤的代碼,無(wú)法解析

首先來(lái)看一段簡(jiǎn)單的代碼

?正確
????????????<asp:Wizard?ID="Wizard1"?runat="server">
????????????????<WizardSteps>
????????????????????<asp:WizardStep?ID="WizardStep1"?runat="server"?Title="Step?1">
????????????????????????21212</asp:WizardStep>
????????????????????<asp:WizardStep?ID="WizardStep2"?runat="server"?Title="Step?2">
????????????????????</asp:WizardStep>
????????????????</WizardSteps>
????????????</asp:Wizard>
????????????錯(cuò)誤
????????????<asp:Wizard?ID="Wizard2"?runat="server">
????????????????<asp:WizardStep?ID="WizardStep1"?runat="server"?Title="Step?1">
????????????????????21212</asp:WizardStep>
????????????????<asp:WizardStep?ID="WizardStep2"?runat="server"?Title="Step?2">
????????????????</asp:WizardStep>
????????????</asp:Wizard>
????????????<br?/>
????????????<br?/>
????????????<asp:Label?ID="Label1"?runat="server"?Text="Label">
????????????????<asp:TextBox?ID="TextBox2"?runat="server"></asp:TextBox>
????????????</asp:Label>
????????????<br?/>
????????????<asp:TextBox?ID="TextBox3"?runat="server">12345</asp:TextBox>
????????????<br?/>
????????????<asp:Label?ID="Label2"?runat="server"?Text="Label">12345</asp:Label>
????????????<br?/>
????????????<br?/>
????????????<asp:TextBox?ID="TextBox1"?runat="server">
????????<asp:Label?runat="server"?Text="Label"></asp:Label>
????????????</asp:TextBox>
Wizard為asp.net2.0新增的一個(gè)控件,這個(gè)頁(yè)面發(fā)生兩個(gè)錯(cuò)誤,如下圖



運(yùn)行此頁(yè)面后則會(huì)報(bào)錯(cuò),出現(xiàn)以下提示

分析器錯(cuò)誤

這里有一個(gè)問(wèn)題,.net提供我們控件時(shí),我們已經(jīng)形成一種定向思維,控件就是那樣寫(xiě)的,如DropDownList,其中只能是套<asp:ListItem>的,那我為什么就不能套別的屬性呢?Wizard控件為什么就要加一個(gè)WizardSteps屬性才可以正常運(yùn)行呢?當(dāng)我們思考到這里,我們就該尋找答案.

2.從ParseChildren元數(shù)據(jù)屬性講起

從第五篇開(kāi)始,我們多次用到了ParseChildren此特性.還請(qǐng)大家先看MSDN對(duì)其的解釋,其有三種情況

(1)ParseChildren(true)???? 第5篇我們使用集合屬性的時(shí)候我們?cè)?jīng)這樣定義,如下代碼

???[ParseChildren(true)]
????public?class?Custom:?Control
????{
????}

(2)ParseChildren(true,"<Default Property>") 第10篇當(dāng)我們定義集合屬性時(shí),我們?cè)@樣定義

DropItemList為集合屬性
???[ParseChildren(true,?"DropItemList")]
???public?class?DropColor:WebControl
????{
???}

(3)ParseChildren(false)? 這個(gè)我們沒(méi)用過(guò),也是我們要講的內(nèi)容,當(dāng)其內(nèi)部定義為flase時(shí),那么放在此控件內(nèi)的元素將被解析成控件,應(yīng)該說(shuō)是頁(yè)分析器ControlBuilder 類(lèi).這里大家可以看看MSDN文檔對(duì)ControlBuilder 類(lèi)的解釋,至少要先知道這一點(diǎn)
默認(rèn)情況下，頁(yè)上的每個(gè)控件都與一個(gè)默認(rèn)的 ControlBuilder 類(lèi)關(guān)聯(lián)。

下面我們慢慢看下來(lái).

3.控件與集合屬性

讓我們?cè)俅位貞浺幌?font face="Courier New">ParseChildren的用法,本次的示例代碼取自asp.net2.0揭密

(1)ParseChildren(true,"<Default Property>")的使用

此控件實(shí)現(xiàn)效果為隨機(jī)顯示一個(gè)內(nèi)部控件內(nèi)容
RItem為一個(gè)繼承Control的控件,其內(nèi)部未實(shí)現(xiàn)任何東西,你可以在其控件內(nèi)部輸出呈現(xiàn),記得上面說(shuō)的ControlBuilder 類(lèi)默認(rèn)關(guān)聯(lián)


示例一
????[ParseChildren(true,?"Items")]
????public?class?ItemRotator?:?CompositeControl
????{
????????private?ArrayList?_items?=?new?ArrayList();

????????[Browsable(false)]
????????public?ArrayList?Items
????????{
????????????get?{?return?_items;?}
????????}

????????protected?override?void?CreateChildControls()
????????{
????????????Random?rnd?=?new?Random();
????????????int?index?=?rnd.Next(_items.Count);
????????????Control?item?=?(Control)_items[index];
????????????this.Controls.Add(item);
????????}
????}

????public?class?RItem?:?Control
????{

????}

頁(yè)面代碼

????<custom:ItemRotator
????????id="ItemRotator1"
????????Runat="server">
????????<custom:ritem?ID="Item1"?runat="server">
????????????First?Item
????????</custom:ritem>
????????<custom:ritem?ID="Item2"?runat="server">
????????????Second?Item
????????????<asp:Calendar
????????????????id="Calendar1"
????????????????Runat="server"?/>
????????</custom:ritem>
????????<custom:ritem?ID="Item3"?runat="server">
????????????Third?Item
????????</custom:ritem>
????</custom:ItemRotator>
????
效果就不說(shuō)了,隨機(jī)顯示ritem控件的內(nèi)容,注意以上控件定義了一個(gè)Items集合屬性

另外改進(jìn)的話就是我們第十篇的講的,為Ritem定義屬性,作為一個(gè)集合屬性,這里就不再列出代碼.

(1)ParseChildren(false)的使用

此控件未添加屬性,而多了一個(gè)方法AddParsedSubObject()

控件有默認(rèn)的頁(yè)面分析邏輯,重寫(xiě)AddParsedSubObject方法,可以向控件添加子控件

示例二

???[ParseChildren(false)]
????public?class?ContentRotator?:?WebControl
????{

????????protected?override?void?AddParsedSubObject(object?obj)
????????{
????????????if?(obj?is?Content)
????????????????base.AddParsedSubObject(obj);
????????}

????????protected?override?void?RenderContents(HtmlTextWriter?writer)
????????{
????????????Random?rnd?=?new?Random();
????????????int?index?=?rnd.Next(this.Controls.Count);
????????????this.Controls[index].RenderControl(writer);
????????}
????}
????[
????ToolboxItem(false)
????]
????public?class?Content?:?Control
????{
????}
頁(yè)面代碼

<custom:ContentRotator
????????id="ContentRotator1"
????????Runat="server">
????????<custom:Content
????????????id="Content1"
????????????Runat="server">
????????????顯示的第一項(xiàng),此不為屬性????
????????</custom:Content>????
????????<custom:Content
????????????id="Content2"
????????????Runat="server">
????????????顯示的第二項(xiàng),此不為屬性
????????????<asp:Calendar
????????????????id="Calendar1"
????????????????Runat="server"?/>????
????????</custom:Content>????
????????<custom:Content
????????????id="Content3"
????????????Runat="server">
????????????顯示的第三項(xiàng),此不為屬性??
????????</custom:Content>??
????</custom:ContentRotator>

注意:ContentRotator無(wú)任何屬性(其內(nèi)部添加的為控件),而是用AddParsedSubObject 方法向控件添加了子控件,而不像ItemRotator控件一樣,其內(nèi)部是屬性而非控件.

4.修改默認(rèn)解析邏輯

上面已經(jīng)說(shuō)過(guò)每個(gè)控件都有默認(rèn)的解析邏輯,其通過(guò)ControlBuilder 類(lèi)來(lái)實(shí)現(xiàn),可以通過(guò)重寫(xiě)其方法來(lái)自定義解析邏輯.下面通過(guò)一個(gè)例子來(lái)說(shuō)明,它把一個(gè)控件以自定義標(biāo)簽所代替

以下列出部分代碼

示例三

????//自定義頁(yè)分析器
????public?class?ServerTabsBuilder?:?ControlBuilder
????{
????????public?override?Type?GetChildControlType(string?tagName,?IDictionary?attribs)
????????{
????????????if?(String.Compare(tagName,?"tab",?true)?==?0)
????????????????return?typeof(ServerTab);
????????????else
????????????????return?null;
????????}
????}

????[ToolboxItem(false)]
????public?class?ServerTab?:?Control
????{
????????private?string?_Text;

????????public?string?Text
????????{
????????????get?{?return?_Text;?}
????????????set?{?_Text?=?value;?}
????????}
????}
(1)ServerTabsBuilder類(lèi)重寫(xiě)了ControlBuilder類(lèi)的
GetChildControlType 方法? 獲取與子標(biāo)記對(duì)應(yīng)的控件類(lèi)型的

(3)最后還需要把控件生成器跟控件關(guān)聯(lián)起來(lái),當(dāng)然還要設(shè)置ParseChildren(false)

????[ControlBuilder(typeof(ServerTabsBuilder))]
????[ParseChildren(false)]
????public?class?ServerTabs?:?WebControl,?IPostBackEventHandler
????{
????}
好了,這里主要代碼就實(shí)現(xiàn)了,呈現(xiàn)代碼大家可在后面下載,下面看下頁(yè)面代碼

<%--以上省略css代碼--%>
????<custom:ServerTabs
????????ID="ServerTabs1"
????????Runat="Server">
????????<tab?Text="First?Tab">
????????<asp:Label?ID="Label1"?runat="server"?Text="Label"></asp:Label>
??????????Contents?of?the?first?tab
????????</tab>????
????????<tab?Text="Second?Tab">
??????????Contents?of?the?second?tab
????????</tab>????
????????<tab?Text="Third?Tab">
??????????Contents?of?the?third?tab
????????</tab>????
????</custom:ServerTabs>

以上鑲套代碼為tab標(biāo)簽,而非<custom:ServerTabs></custom:ServerTabs>,但實(shí)現(xiàn)效果是一樣的,只是我們改了默認(rèn)的頁(yè)分析邏輯,自定義了控件頁(yè)生成器(分析器)
看下效果(當(dāng)重新編譯后需要重新啟動(dòng)vs2005才能看到效果)




好了,這次的主題也講完了,這里需要注意的是asp.net2.0中復(fù)合控件只需要繼承CompositeControl類(lèi)即可.

這里預(yù)祝大家國(guó)慶快樂(lè).

示例代碼下載

下一篇將對(duì)此系列寫(xiě)下來(lái)的十四篇文章進(jìn)行一個(gè)小結(jié),并進(jìn)行補(bǔ)充,當(dāng)然小結(jié)并非是結(jié)束,接著我們還會(huì)繼續(xù)討論模板以及更多.希望大家喜歡.

轉(zhuǎn)自:

轉(zhuǎn)載于:https://www.cnblogs.com/pro_net/archive/2009/03/21/1418712.html

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