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asp 语法教程(五)asp 的服务器端编程控件篇

2008-02-23 05:37:44来源：互联网阅读 ()

使用定制的服务器控件
在asp 中提供了45个已经做好了的服务器控件，我们可以将他们象黑盒子一样的使用。除此以外，开发者还可以使用任何第三方开发的服务器控件
在下面的例子中，我们要用到一个通过<acme:calendar runat=server>标签声明的组件，请注意，在文件的第一行必须使用<% Register %> 来声明 "Acme Xml "标签的的前缀"Acme".在asp 文件中，将会使用这个命名的服务器控件的类的实例。
<%@ Register TagPrefix="Acme" Namespace="Acme" %>

<html>
<head>
<link rel="stylesheet"href="intro.css">
</head>

<script language="VB" runat=server>

Sub SubmitBtn_Click(Sender As Object, E As EventArgs)
Message.Text = "Hi " & Name.Text & ", you selected: " & Category.SelectedItem.Text & " on: " & MyCal.Date
End Sub

</script>

<body>

<center>

<form action="intro7.aspx" method="post" runat="server">

<asp:adrotator AdvertisementFile="ads.xml" BorderColor="black" BorderWidth=1 runat="server"/>

<h3> Name: <asp:textbox id="Name" runat="server"/>

Category: <asp:dropdownlist id="Category" runat=server>
<asp:listitem >psychology</asp:listitem>
<asp:listitem >business</asp:listitem>
<asp:listitem >popular_comp</asp:listitem>
</asp:dropdownlist>

<asp:button type=submit text="Lookup" OnClick="SubmitBtn_Click" runat="server"/>

<p>

<Acme:Calendar id="MyCal" runat=server/>

<p>

<asp:label id="Message" runat="server"/>

</form>

</center>

</body>
</html>

声明Acme 的文件
using System;
using System.Web;
using System.Web.UI;
using System.Collections;

namespace Acme
{
public class Calendar : Control, IPostBackEventHandler, IPostBackDataHandler
{
private String[] monthNames = new String[12];
private DateTime currentDate = DateTime.Now;
private String backColor = "#dcdcdc";
private String foreColor = "#eeeeee";

protected override void Init()
{
// Todo: We should remove the need to call this
Page.RegisterRequiresPostBack(this);
Page.RegisterPostBackScript();

currentDate = DateTime.Now;

// Todo: Hack needed because COOL doesn't support array initializers yet
monthNames[0] = "January";
monthNames[1] = "February";
monthNames[2] = "March";
monthNames[3] = "April";
monthNames[4] = "May";
monthNames[5] = "June";
monthNames[6] = "July";
monthNames[7] = "August";
monthNames[8] = "September";
monthNames[9] = "October";
monthNames[10] = "November";
monthNames[11] = "December";
}

protected override void LoadState(Object viewState)
{
// If we've done a post-back, the old date will be available to us

if (null != viewState)
{
currentDate = DateTime.Parse((String) viewState);
}
}

public void RaisePostBackEvent(String eventArgument)
{
//Page.Response.Write("RaisePostBackEvent Called!!!");

if (eventArgument == null)
{
return;
}

// Keep track of old date (for event firing purposes)

DateTime oldDate = currentDate;

// Todo: We should have post-back take two arguments: eventname and eventarguments

if (String.Compare("NavNextMonth", eventArgument, true) == 0)
{
currentDate = currentDate.AddMonths(1);
}
else if (String.Compare("NavPrevMonth", eventArgument, true) == 0)
{
currentDate = currentDate.AddMonths(-1);
}
else
{
int daySelected = Int32.Parse(eventArgument);
currentDate = new DateTime(currentDate.Year, currentDate.Month, daySelected);
}
}

protected override Object SaveState()
{
// Save CurrentDate out as view state for postback scenarios

return currentDate.ToString();
}

protected override void Render(HtmlTextWriter output)
{
//Response.Write(Page.Request.UserAgent);

if (Page.Request.UserAgent.IndexOf("MSIE 5.5") != -1)
RenderUpLevel(output);
else
RenderDownLevel(output);
}

protected void RenderUpLevel(HtmlTextWriter output)
{
output.WriteLine("<input name='" UniqueID "_CurrentDate' id='" UniqueID "_CurrentDate' type=hidden>");
output.WriteLine("<span id='" UniqueID "'></span>");

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