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asp+语法教程(五)asp+的服务器端编程控件篇

　2000-11-09 09:49:53　来源：WEB开发网　　　

核心提示：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，asp+语法教程(五)asp+的服务器端编程控件篇，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，开发者不需要关心客户浏览器是高级的还是低级的，日历控件自己会处理两种浏览器之间的差别下一讲，

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>");
output.WriteLine("<script language=jscript>drawcalendar('" + UniqueID + "', '" + Int32.Format(currentDate.Year, null) + "/" + Int32.Format(currentDate.Month, null) + "/" + Int32.Format(currentDate.Day, null) + "');</script>");
}

protected override void PreRender()
{
String DHTMLFunction = "";

DHTMLFunction += "<script language='javaScript'> \n";
DHTMLFunction += " function drawcalendar(calname, newDate) \n";
DHTMLFunction += " { \n";
DHTMLFunction += " var CurrentDate = new Date(newDate);\n";
DHTMLFunction += " var MonthArray = new Array('January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December');\n";
DHTMLFunction += " var MonthDays = new Array(31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);\n";
DHTMLFunction += " var calText;\n";
DHTMLFunction += " calText = '<table bgcolor=#dcdcdc border=0 height=190 valign=top>';\n";
DHTMLFunction += " calText = calText + '<tr><td>';\n";
DHTMLFunction += " calText = calText + '<center>';\n";
DHTMLFunction += " calText = calText + \"<a href='Javascript:drawcalendar(\\\"\" + calname + \"\\\", \\\"\" + CurrentDate.getFullYear() + \"/\" + CurrentDate.getMonth() + \"/\" + CurrentDate.getDate() + \"\\\")'>\";\n";
DHTMLFunction += " calText = calText + '<img src=http://www.cncms.com/quickstart/aspplus/images/left4.gif width=11 height=11 border=0></a>';\n";
DHTMLFunction += " calText = calText + ' <b>' + MonthArray[CurrentDate.getMonth()] + ' ' + CurrentDate.getFullYear() + '</b>';\n";
DHTMLFunction += " calText = calText + \" <a href='javascript:drawcalendar(\\\"\" + calname + \"\\\", \\\"\" + CurrentDate.getFullYear() + \"/\" + (CurrentDate.getMonth() + 2) + \"/\" + CurrentDate.getDate() + \"\\\")'>\";\n";
DHTMLFunction += " calText = calText + '<IMG SRC=http://www.cncms.com/quickstart/aspplus/images/right4.gif width=11 height=11 border=0></a>';\n";
DHTMLFunction += " calText = calText + '</center>';\n";
DHTMLFunction += " calText = calText + '</td></tr>';\n";
DHTMLFunction += " calText = calText + '<tr valign=top><td valign=top>';\n";
DHTMLFunction += " calText = calText + '<table border=1 bgcolor=#eeeeee height=160>';\n";
DHTMLFunction += " calText = calText + '<tr height=20>';\n";
DHTMLFunction += " calText = calText + ' <td align=right width=23> Sun </td>';\n";
DHTMLFunction += " calText = calText + ' <td align=right width=23> Mon </td>';\n";
DHTMLFunction += " calText = calText + ' <td align=right width=23> Tue </td>';\n";
DHTMLFunction += " calText = calText + ' <td align=right width=23> Wed </td>';\n";
DHTMLFunction += " calText = calText + ' <td align=right width=23> Thu </td>';\n";
DHTMLFunction += " calText = calText + ' <td align=right width=23> Fri </td>';\n";
DHTMLFunction += " calText = calText + ' <td align=right width=23> Sat </td>';\n";
DHTMLFunction += " calText = calText + '</tr>';\n";
DHTMLFunction += " calText = calText + '<tr>';\n";
DHTMLFunction += " var numDays = MonthDays[CurrentDate.getMonth()];\n";
DHTMLFunction += " var firstDay = new Date(1999, 8, 1).getDay();\n";
DHTMLFunction += " for (var x=0; x<firstDay; x++)\n";
DHTMLFunction += " {\n";
DHTMLFunction += " calText = calText + '<td align=right width=23></td>'\n";
DHTMLFunction += " }\n";
DHTMLFunction += " for (var x=1; x<=numDays; x++) \n";
DHTMLFunction += " { \n";
DHTMLFunction += " if (CurrentDate.getDate() == x) \n";
DHTMLFunction += " { \n";
DHTMLFunction += " calText = calText + '<td align=right width=23>';\n";
DHTMLFunction += " calText = calText + '<font color=red><b><u>' + x + '</u></b></font>';\n";
DHTMLFunction += " calText = calText + '</td>';\n";
DHTMLFunction += " }\n";
DHTMLFunction += " else \n";
DHTMLFunction += " { \n";
DHTMLFunction += " calText = calText + '<td align=right width=23>';\n";
DHTMLFunction += " calText = calText + \"<a href='javascript:drawcalendar(\\\"\" + calname + \"\\\", \\\"\" + CurrentDate.getFullYear() + \"/\" + (CurrentDate.getMonth()+1) + \"/\" + x + \"\\\")'>\" + x + \"</a>\";";
DHTMLFunction += " calText = calText + '</td>';\n";
DHTMLFunction += " }\n";
DHTMLFunction += " if (((firstDay+x) % 7) == 0)\n";
DHTMLFunction += " {\n";
DHTMLFunction += " calText = calText + '</tr><tr>';\n";
DHTMLFunction += " }\n";
DHTMLFunction += " }\n";
DHTMLFunction += " calText = calText + '</tr>';";
DHTMLFunction += " calText = calText + '</table></td></tr></table>';";
DHTMLFunction += " var CalendarSpan = document.all(calname);";
DHTMLFunction += " if (CalendarSpan != null)";
DHTMLFunction += " CalendarSpan.innerHTML = calText;";
DHTMLFunction += " var CalendarValue = document.all(calname + '_CurrentDate');";
DHTMLFunction += " if (CalendarValue != null)";
DHTMLFunction += " CalendarValue.value = '' + (CurrentDate.getMonth() + 1) + '/' + CurrentDate.getDate() + '/' + CurrentDate.getFullYear();";
DHTMLFunction += " } \n";
DHTMLFunction += "</script>\n";

if (Page.Request.UserAgent.IndexOf("MSIE 5.5") != -1)
Page.RegisterClientScriptBlock("ACME_CALENDAR_DHTML", DHTMLFunction);
}

protected void RenderDownLevel(HtmlTextWriter output)
{
// Output Calendar Header

output.WriteLine("<table bgcolor=" + backColor + " border=0 height=190 valign=top><tr><td>");
output.WriteLine("<table bgcolor=" + backColor + " border=0 height=190 valign=top>");
output.WriteLine("<tr><td>");
output.WriteLine("<center>");
output.WriteLine(" <a href=\"javascript:" + Page.GetPostBackEventReference(this, "NavPrevMonth") + "\">");
output.WriteLine("<img src=http://www.cncms.com/quickstart/aspplus/images/left4.gif width=11 height=11 border=0></a>");
output.WriteLine(" <b>" + monthNames[currentDate.Month-1] + " " + Int32.Format(currentDate.Year, null) + "</b>");
output.WriteLine(" <a href=\"javascript:" + Page.GetPostBackEventReference(this, "NavNextMonth") + "\">");
output.WriteLine("<IMG SRC=http://www.cncms.com/quickstart/aspplus/images/right4.gif width=11 height=11 border=0></a>");
output.WriteLine("</center>");
output.WriteLine("</td></tr>");
output.WriteLine("<tr valign=top><td valign=top>");
output.WriteLine("<table border=1 bgcolor=" + foreColor + " height=160>");
output.WriteLine("<tr height=20>");
output.WriteLine(" <td align=right width=23> Sun </td>");
output.WriteLine(" <td align=right width=23> Mon </td>");
output.WriteLine(" <td align=right width=23> Tue </td>");
output.WriteLine(" <td align=right width=23> Wed </td>");
output.WriteLine(" <td align=right width=23> Thu </td>");
output.WriteLine(" <td align=right width=23> Fri </td>");
output.WriteLine(" <td align=right width=23> Sat </td>");
output.WriteLine("</tr>");
output.WriteLine("<tr>");

// Calculate how many days are in the month

int numDays = DateTime.DaysInMonth(currentDate.Year, currentDate.Month);

// Calculate what day of week the first day of the month is on

int firstDay = new DateTime(currentDate.Year, currentDate.Month, 1).DayOfWeek;

// Pre-Day Padding

for (int x=0; x<firstDay; x++)
{
output.WriteLine("<td align=right width=23></td>");
}

// Output each day

for (int x=1; x<=numDays; x++)
{
if (currentDate.Day == x)
{
output.Write("<td align=right width=23>");
output.Write("<font color=red><b><u>" + Int32.Format(x, null) + "</u></b></font>");
output.WriteLine("</td>");
}
else
{
output.Write("<td align=right width=23>");
output.Write("<a href=\"javascript:" + Page.GetPostBackEventReference(this, Int32.Format(x, null)) + "\">");
output.Write(Int32.Format(x, null) + "</a>");
output.WriteLine("</td>");
}

// PerPage row break as appropriate
if (((firstDay+x) % 7) == 0)
{
output.WriteLine("</tr><tr>");
}
}

output.WriteLine("</tr>");
output.WriteLine("</table></td></tr></table></table>");
}

public DateTime Date
{
get
{
return currentDate;
}
set
{
currentDate = value;
}
}

public String BackColor
{
get
{
return backColor;
}
set
{
backColor = value;
}
}

public String ForeColor
{
get
{
return foreColor;
}
set
{
foreColor = value;
}
}

// Todo: We should eliminate the need for a control developer to do stub
// implementations of the below standard IPostDataHandler Methods

public bool LoadPostData(String postDataKey, NameValueCollection values)
{
String clientDate = values[UniqueID + "_CurrentDate"];

if (clientDate != null)
currentDate = DateTime.Parse(clientDate);

return false;
}

public void RaisePostDataChangedEvent()
{

}
}
}

生成服务器控件的文件

csc /t:library /r:System.Web.dll /r:System.dll /out:..\..\..\bin\Acme.dll Acme.cs
csc /t:library /out:..\..\..\bin\WebMarket.dll WebMarket.cs

这个例子的演示在
http://tutorial.superexpert.com/quickstart/aspplus/samples/webforms/intro/intro7.aspx
这个日历的服务器控件可以同时支持高级和低级的浏览器，对于高级的浏览器，他在客户端生成DHTML 代码，DHTML 文档不需要和服务器进行交互！对于低级的浏览器，则生成标准的 HTML 3.2 的代码，这个时候需要和服务器的交互来处理浏览器客户端的用户操作
注意：这个页面的代码的开发者在书写的过程中，开发者不需要关心客户浏览器是高级的还是低级的。日历控件自己会处理两种浏览器之间的差别
下一讲，我们将要进入asp+ 操作数据库的章节，请大家随时留意我们的站点更新！