asp.net控件开发基础(1) - 军军小站|张军博客

asp.net本身提供了很多控件,提供给我们这些比较懒惰的人使用,我认为控件的作用就在此,因为我们不想重复工作,所以要创建它,这个本身便是一个需求的关系,所以学习控件开发很有意思.

wrox网站上有本书 Professional ASP.NET 2.0 Server Control and Component Development

现在还没有出版,但网站上放出了代码,所以正好下载过来学习一下.

我看过前几章代码,环环相扣,作者用不同的知识向我们展示同一个效果,所以循序渐进的学下来很有好处.

虽然自己对控件开发还不是很熟悉，但我感觉以下几点很重要，是我自己总结的

1.了解控件之间的继承关系

最好是先看看看System.Web.UI命名空间

(1)Control 类，所有的控件都共享的一个类，你需要去看下其里面受保护的几个方法和属性，虽然一下看不完，以后会发现常常用到这些方法

大家可以在MSDN看一下其派生类

(2)HtmlTextWriter 类

不得不了解的一个类，主要工作就是我们写的标记字符和文本输出

2.重写方法

(1) 必须继承Control类
(2) 重写Control类的Render方法，这个是必须的，因为其他控件都继承了Control 类类，所以几乎所有控件都有这个方法

3.熟悉元数据

大家都知道asp.net控件属性在编辑器上是分类的，如外观，行为，布局等，每个属性还给出了解释

简单的元数据就是起到这个作用，当然你也可以不加，但使用了元数据让人感到有亲切感，写法如
下
[CategoryAttribute("Appearance")]

要使用元数据，必须引用System.ComponentModel命名控件，一般你如果写组件的话，不可能不用到这样类库。具体的MSDN上有所介绍。

一.输出字符串
说多了没意思，还是来演练吧。首先你得了解HTML。来看下面代码,效果就是输出HTML到客户端

示例一

using System;

using System.Web.UI;

namespace CustomComponents

{

/// <summary>

/// SummarydescriptionforCreditCardForm

/// </summary>

public class CreditCardForm1:Control

{

protected override void Render(HtmlTextWriterwriter)

{

writer.Write( " <tablestyle='width:287px;height:124px;border-width:0;'> " );

writer.Write( " <tr> " );

writer.Write( " <td><strong>PaymentMethod</strong></td> " );

writer.Write( " <td> " );

writer.Write( " <selectname='PaymentMethod'id='PaymentMethod'style='width:100%;'> " );

writer.Write( " <optionvalue='0'>Visa</option> " );

writer.Write( " <optionvalue='1'>MasterCard</option> " );

writer.Write( " </select> " );

writer.Write( " </td> " );

writer.Write( " </tr> " );

writer.Write( " <tr> " );

writer.Write( " <td><strong>CreditCardNo.</strong></td> " );

writer.Write( " <td><inputname='CreditCardNo'id='CreditCardNo'type='text'/></td> " );

writer.Write( " </tr> " );

writer.Write( " <tr> " );

writer.Write( " <td><strong>Cardholder'sName</strong></td> " );

writer.Write( " <td><inputname='CardholderName'id='CardholderName'type='text'/></td> " );

writer.Write( " </tr> " );

writer.Write( " <tr> " );

writer.Write( " <td><strong>ExpirationDate</strong></td> " );

writer.Write( " <td> " );

writer.Write( " <selectname='Month'id='Month'> " );

for ( int day = 1 ;day < 13 ;day ++ )

{

if (day < 10 )

writer.Write( " <optionvalue=' " + day.ToString() + " '> " + " 0 " + day.ToString() + " </option> " );

else

writer.Write( " <optionvalue=' " + day.ToString() + " '> " + day.ToString() + " </option> " );

}

writer.Write( " </select> " );

writer.Write( " &nbsp " );

writer.Write( " <selectname='Year'id='Year'> " );

for ( int year = 2005 ;year < 2015 ;year ++ )

{

writer.Write( " <optionvalue=' " + year.ToString() + " '> " + year.ToString() + " </option> " );

}

writer.Write( " </select> " );

writer.Write( " </td> " );

writer.Write( " </tr> " );

writer.Write( " <tr> " );

writer.Write( " <tdalign='center'colspan='2'> " );

writer.Write( " <inputtype='submit'value='Submit'/> " );

writer.Write( " </td> " );

writer.Write( " </tr> " );

writer.Write( " </table> " );

base .Render(writer);

}

效果很简单,其实就一直在输出HTML再加几个属性,大家可以直接把代码放在App_Code文件夹里,就可自动编译,当然也可以创建web控件库.
注意要继承Control类,重写Render方法,用HtmlTextWriter类的Write输出HTML

使用控件

(1).需要先注册一下

<%@ Register TagPrefix="custom" Namespace="CustomComponents" %>

(2) 然后就使用标签输出效果

<custom:CreditCardForm1 runat="server" ID="ccf" />

下为效果图

二.改善,加入属性和元数据

可能上面做出的控件毫无用处,但却可以让你熟悉一下步骤,上面的控件定的很死,没有定义任何属性,用处不大,下面来改造

我们来定义常用属性,然后再输出,这样我们就可以修改控件的属性了,

示例二

using System;

using System.Web.UI;

using System.ComponentModel;

namespace CustomComponents

{

[DefaultPropertyAttribute( " CardholderNameText " )]

[ToolboxData( @" <{0}:CreditCardForm2

PaymentMethodText='信用卡类型'CreditCardNoText='信用卡卡号'

CardholderNameText='信用卡持有者姓名'SubmitButtonText='提交'

runat='server'></{0}:CreditCardForm2> " )

]

public class CreditCardForm2:Control

{

private string paymentMethodText = " 信用卡类型 " ;

private string creditCardNoText = " 信用卡卡号 " ;

private string cardholderNameText = " 信用卡持有者姓名 " ;

private string expirationDateText = " 最后使用时间 " ;

private string submitButtonText = " 提交 " ;

[BrowsableAttribute( true )]

[DescriptionAttribute( " 获取和设置信用卡类型 " )]

[DefaultValueAttribute( " 信用卡类型 " )]

[CategoryAttribute( " Appearance " )]

public virtual string PaymentMethodText

{

get { return this .paymentMethodText;}

set { this .paymentMethodText = value;}

}

[BrowsableAttribute( true )]

[DescriptionAttribute( " 获取或设置信用卡卡号 " )]

[DefaultValueAttribute( " 信用卡卡号 " )]

[CategoryAttribute( " Appearance " )]

public virtual string CreditCardNoText

{

get { return this .creditCardNoText;}

set { this .creditCardNoText = value;}

}

[BrowsableAttribute( true )]

[DescriptionAttribute( " 获取或设置信用卡持有者姓名 " )]

[DefaultValueAttribute( " 信用卡持有者姓名 " )]

[CategoryAttribute( " Appearance " )]

public virtual string CardholderNameText

{

get { return this .cardholderNameText;}

set { this .cardholderNameText = value;}

}

[BrowsableAttribute( true )]

[DescriptionAttribute( " 获取或设置最后使用时间 " )]

[DefaultValueAttribute( " 最后使用时间 " )]

[CategoryAttribute( " Appearance " )]

public virtual string ExpirationDateText

{

get { return this .expirationDateText;}

set { this .expirationDateText = value;}

}

[BrowsableAttribute( true )]

[DescriptionAttribute( " 获取或设置按钮标签 " )]

[DefaultValueAttribute( " 提交 " )]

[CategoryAttribute( " Appearance " )]

public virtual string SubmitButtonText

{

get { return this .submitButtonText;}

set { this .submitButtonText = value;}

}

protected override void Render(HtmlTextWriterwriter)

{

writer.Write( " <tablestyle='width:287px;height:124px;border-width:0;'> " );

writer.Write( " <tr> " );

writer.Write( " <td> " + PaymentMethodText + " </td> " );

writer.Write( " <td> " );

writer.Write( " <selectname='PaymentMethod'id='PaymentMethod'style='width:100%;'> " );

writer.Write( " <optionvalue='0'>Visa</option> " );

writer.Write( " <optionvalue='1'>MasterCard</option> " );

writer.Write( " </select> " );

writer.Write( " </td> " );

writer.Write( " </tr> " );

writer.Write( " <tr> " );

writer.Write( " <td> " + CreditCardNoText + " </td> " );

writer.Write( " <td><inputname='CreditCardNo'id='CreditCardNo'type='text'/></td> " );

writer.Write( " </tr> " );

writer.Write( " <tr> " );

writer.Write( " <td> " + CardholderNameText + " </td> " );

writer.Write( " <td><inputname='CardholderName'id='CardholderName'type='text'/></td> " );

writer.Write( " </tr> " );

writer.Write( " <tr> " );

writer.Write( " <td> " + ExpirationDateText + " </td> " );

writer.Write( " <td> " );

writer.Write( " <selectname='Month'id='Month'> " );

for ( int day = 1 ;day < 13 ;day ++ )

{

if (day < 10 )

writer.Write( " <optionvalue=' " + day.ToString() + " '> " + " 0 " + day.ToString() + " </option> " );

else

writer.Write( " <optionvalue=' " + day.ToString() + " '> " + day.ToString() + " </option> " );

}

writer.Write( " </select> " );

writer.Write( " &nbsp " );

writer.Write( " <selectname='Year'id='Year'> " );

for ( int year = 2005 ;year < 2015 ;year ++ )

{

writer.Write( " <optionvalue=' " + year.ToString() + " '> " + year.ToString() + " </option> " );

}

writer.Write( " </select> " );

writer.Write( " </td> " );

writer.Write( " </tr> " );

writer.Write( " <tr> " );

writer.Write( " <tdalign='center'colspan='2'> " );

writer.Write( " <inputtype='submit'value=' " + SubmitButtonText + " '/> " );

writer.Write( " </td> " );

writer.Write( " </tr> " );

writer.Write( " </table> " );

base .Render(writer);

}

上面我们接触到了元数据了,意思应该很好理解,为了测试元数据的作用,大家可以新建一个类库项目,然后把写的代码放这个项目里面,接着web网站引用这个项目,成功生成以后,你会发现工具箱已经自动帮你加上了这几个控件

接着你要做的工作就是拖动你需要的控件,然后你会在属性面板看到下图

然后你再结合代码中的元数据,应该就知道大概意思了.(可以根据你的理解结合MSDN看)

三.再次改善,淘汰用Write方法以字符串的方式输出HTML

接着我们继续发现问题,我们发现我们除了定义几个需要自己来修改的属性外,还是要用来大量的字符串用来输出HTML,而且容易输错.所以HtmlTextWriter类提供几个有用的方法用来代替.

(1)AddStyleAttribute方法为标签添加样式属性
(2)AddAttribute方法为标签添加属性
(3)RenderBeginTag 开始写入标签头如<table....>
(4)RenderEndTag 写入标签尾部,如</table>

这里有几点需要特别注意.

一.因为其定义方式跟我们平时定义方式不同,我们平时写HTML时,是先写标签开头,再写标签的属性.如<table borderwidth="0">,然而我们在使用上面几个方法时,需要有先后顺序, 我们需要先定义标签的属性和样式, 然后再输出标签头.

二.标签头和尾,需一一对应.可以理解为嵌套关系.最好的理解方法就是输出代码后,查看源文件,再结合原来定义的代码来看.

还是看代码比较容易说明,由于CreditCardForm2已经定义了我们需要的属性,而我们现在要做的只是用标签的形式来替代字符串的形式,所以只需要继承CreditCardForm2类,重写Render方法即可

示例三

protected override void Render(HtmlTextWriterwriter)

{

writer.AddStyleAttribute(HtmlTextWriterStyle.BorderWidth, " 0 " );

writer.RenderBeginTag(HtmlTextWriterTag.Table);

writer.RenderBeginTag(HtmlTextWriterTag.Tr);

writer.RenderBeginTag(HtmlTextWriterTag.Td);

writer.Write( " <strong> " + PaymentMethodText + " </strong> " );

writer.RenderEndTag();

writer.RenderBeginTag(HtmlTextWriterTag.Td);

writer.AddAttribute(HtmlTextWriterAttribute.Name, " PaymentMethod " );

writer.AddAttribute(HtmlTextWriterAttribute.Id, " PaymentMethod " );

writer.AddStyleAttribute(HtmlTextWriterStyle.Width, " 100% " );

writer.RenderBeginTag(HtmlTextWriterTag.Select);

writer.AddAttribute(HtmlTextWriterAttribute.Value, " 0 " );

writer.RenderBeginTag(HtmlTextWriterTag.Option);

writer.Write( " Visa " );

writer.RenderEndTag();

writer.AddAttribute(HtmlTextWriterAttribute.Value, " 1 " );

writer.RenderBeginTag(HtmlTextWriterTag.Option);

writer.Write( " MasterCard " );

writer.RenderEndTag();

writer.RenderBeginTag(HtmlTextWriterTag.Tr);

writer.RenderBeginTag(HtmlTextWriterTag.Td);

writer.Write( " <strong> " + CreditCardNoText + " </strong> " );

writer.RenderEndTag();

writer.RenderBeginTag(HtmlTextWriterTag.Td);

writer.AddAttribute(HtmlTextWriterAttribute.Name, " CreditCardNo " );

writer.AddAttribute(HtmlTextWriterAttribute.Id, " CreditCardNo " );

writer.AddAttribute(HtmlTextWriterAttribute.Type, " text " );

writer.RenderBeginTag(HtmlTextWriterTag.Input);

writer.RenderEndTag();

writer.RenderBeginTag(HtmlTextWriterTag.Tr);

writer.RenderBeginTag(HtmlTextWriterTag.Td);

writer.Write( " <strong> " + CardholderNameText + " </strong> " );

writer.RenderEndTag();

writer.RenderBeginTag(HtmlTextWriterTag.Td);

writer.AddAttribute(HtmlTextWriterAttribute.Name, " CardholderName " );

writer.AddAttribute(HtmlTextWriterAttribute.Id, " CardholderName " );

writer.AddAttribute(HtmlTextWriterAttribute.Type, " text " );

writer.RenderBeginTag(HtmlTextWriterTag.Input);

writer.RenderEndTag();

writer.RenderBeginTag(HtmlTextWriterTag.Tr);

writer.RenderBeginTag(HtmlTextWriterTag.Td);

writer.Write( " <strong> " + ExpirationDateText + " </strong> " );

writer.RenderEndTag();

writer.RenderBeginTag(HtmlTextWriterTag.Td);

writer.AddAttribute(HtmlTextWriterAttribute.Name, " Month " );

writer.AddAttribute(HtmlTextWriterAttribute.Id, " Month " );

writer.RenderBeginTag(HtmlTextWriterTag.Select);

for ( int day = 1 ;day < 13 ;day ++ )

{

writer.AddAttribute(HtmlTextWriterAttribute.Value,day.ToString());

writer.RenderBeginTag(HtmlTextWriterTag.Option);

if (day < 10 )

writer.Write( " 0 " + day.ToString());

else

writer.Write(day);

writer.RenderEndTag();

}

writer.RenderEndTag();

writer.Write( "   " );

writer.AddAttribute(HtmlTextWriterAttribute.Name, " Year " );

writer.AddAttribute(HtmlTextWriterAttribute.Id, " Year " );

writer.RenderBeginTag(HtmlTextWriterTag.Select);

for ( int year = 2005 ;year < 2015 ;year ++ )

{

writer.AddAttribute(HtmlTextWriterAttribute.Value,year.ToString());

writer.RenderBeginTag(HtmlTextWriterTag.Option);

writer.Write(year);

writer.RenderEndTag();

}

writer.RenderEndTag();

writer.RenderBeginTag(HtmlTextWriterTag.Tr);

writer.AddAttribute(HtmlTextWriterAttribute.Align, " center " );

writer.AddAttribute(HtmlTextWriterAttribute.Colspan, " 2 " );

writer.RenderBeginTag(HtmlTextWriterTag.Td);

writer.AddAttribute(HtmlTextWriterAttribute.Type, " submit " );

writer.AddAttribute(HtmlTextWriterAttribute.Value,SubmitButtonText);

writer.RenderBeginTag(HtmlTextWriterTag.Input);

writer.RenderEndTag();

}

实现的效果虽然一样,但上面的代码是不是漂亮很多,而且不容易输错.这也是所提倡的做法

四.未使用视图状态的后果

还是视图状态,关于视图状态大家可以参考MSDN和相关文章

看以下的示例,还是CreditCardForm3这个控件

if ( ! IsPostBack)

{

creditcardform.CardholderNameText = " FullName " ;

creditcardform.CreditCardNoText = " CreditCardNo " ;

creditcardform.ExpirationDateText = " ExpirationDate " ;

creditcardform.PaymentMethodText = " PaymentOptions " ;

creditcardform.SubmitButtonText = " Send " ;

}

首次加载效果

点击按钮以后

五.使用视图状态改善效果

前提条件是你未禁用视图状态

继承CreditCardForm3,改写每个属性

public override string PaymentMethodText

{

get { return ViewState[ " PaymentMethodText " ] != null ? ( string )ViewState[ " PaymentMethodText " ]: " 信用卡类型 " ;}

set {ViewState[ " PaymentMethodText " ] = value;}

}

public override string CreditCardNoText

{

get { return ViewState[ " CreditCardNoText " ] != null ? ( string )ViewState[ " CreditCardNoText " ]: " 信用卡卡号 " ;}

set {ViewState[ " CreditCardNoText " ] = value;}

}

public override string CardholderNameText

{

get { return ViewState[ " CardholderNameText " ] != null ? ( string )ViewState[ " CardholderNameText " ]: " 信用卡持有者姓名 " ;}

set {ViewState[ " CardholderNameText " ] = value;}

}

public override string ExpirationDateText

{

get { return ViewState[ " ExpirationDateText " ] != null ? ( string )ViewState[ " ExpirationDateText " ]: " 最后使用时间 " ;}

set {ViewState[ " ExpirationDateText " ] = value;}

}

public override string SubmitButtonText

{

get { return ViewState[ " SubmitButtonText " ] != null ? ( string )ViewState[ " SubmitButtonText " ]: " 提交 " ;}

set {ViewState[ " SubmitButtonText " ] = value;}

}

以上全为个人见解,如有错误,希望大家指出.

点击下载代码

http://www.wrox.com/WileyCDA/WroxTitle/productCd-0471793507.html asp.net 2.0控件开发

所有相关文章地址: http://www.cnblogs.com/Clingingboy/category/68883.html?Show=All

asp.net控件开发基础(1)

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