转TerreyLee AJAX入门系列2——ScriptManager的理解总结
ScriptManager的功能之一就是处理页面上局部更新，对于这点，我想大家都知道。但是他工作的原理到底是什么呢，这个暂且不从正面来回答。
我们这样想一下，目前能够真正实现局部刷新的就是js+xml+dom等编写的ajax代码，而ScriptManager竟然也能实现局部刷新，必然是通过什么手段最终转化成了js等的ajax代码。这种猜想我们从哪里去验证一下呢，且看下面。
1.下面引用了TerreyLee的例子，稍作改动后如下，没有带任何Ajax控件
前台代码： <form id="form1" runat="server">
<div>
<asp:Calendar ID="Calendar1" runat="server"></asp:Calendar>
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="true" onselectedindexchanged="DropDownList1_SelectedIndexChanged">
<asp:ListItem Value="0">==请选择==</asp:ListItem>
<asp:ListItem Value="1">Red</asp:ListItem>
<asp:ListItem Value="2">Yellow</asp:ListItem>
<asp:ListItem Value="3">Green</asp:ListItem>
</asp:DropDownList>
</div>
</form> 后台代码： protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e) { Calendar1.DayStyle.BackColor = System.Drawing.Color.FromName(DropDownList1.SelectedItem.Text); }
运行结果：
看到状态栏带有刷新进度条。
查看一下服务器端返回的源文件：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head><title> </title></head> <body> <form name="form1" method="post" action="Default.aspx" id="form1"> <div> <input type="hidden" name="__EVENTTARGET" id="__EVENTTARGET" value="" /> <input type="hidden" name="__EVENTARGUMENT" id="__EVENTARGUMENT" value="" /> <input type="hidden" name="__LASTFOCUS" id="__LASTFOCUS" value="" /> <input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwUKLTkxMjIzNTI5NQ9kFgICAw9kFgICAw8QZGQWAWZkZJtbkkCYOre8ffrFCqW5LPWkPTtr" /> </div> <script type="text/javascript"> //<![CDATA[ var theForm = document.forms['form1']; if (!theForm) { theForm = document.form1; } function __doPostBack(eventTarget, eventArgument) { if (!theForm.onsubmit || (theForm.onsubmit() != false)) { theForm.__EVENTTARGET.value = eventTarget; theForm.__EVENTARGUMENT.value = eventArgument; theForm.submit(); } } //]]> </script> <div> <input type="hidden" name="__EVENTVALIDATION" id="__EVENTVALIDATION" value="/wEWMgLIi4jfDQLd2/zADgK38ereCQLa96nuBQLa94WJDQLa9/GkBgLa9+3fDwLa99l6Atr39cMFAtr34f4OApeUoIgLApeUnKMMApeUiN4FApeU5PkOApeU0JQGApeUzM8PApeUuGsCl5SUhggCl5TA7g4Cl5S8igYC8q3OkgEC8q26zgoC8q2W6QMC8q2ChAsC8q3+vwwC8q3q2gUC8q3G9Q4C8q2ykQYC8q3u+QQC8q3alAwC7brsvQ8C7brYWALturT0CQLtuqCvAQLtupzKCgLtuojlAwLtuuSACwLtutC7DALtuoyEAQLtuvi/CgLI04vIBQLI0+fjDgLI09OeBgLI08+5DwLI07tVAp3kj+UKAo2LpYsGApKLpYsGApOLpYsGApCLpYsGdr/l7ekdPMwRDZCnhQ2pPfOpOcI=" /> </div> <div> <SPAN style="COLOR: #ff0000"><SPAN style="COLOR: #339966"> <table id="Calendar1“>...</table> </SPAN> <select name="DropDownList1" onchange="javascript:setTimeout('__doPostBack(\'DropDownList1\',\'\')', 0)" id="DropDownList1"> <option selected="selected" value="0">==请选择==</option> <option value="1">Red</option> <option value="2">Yellow</option> <option value="3">Green</option> </select> </SPAN> </div> </form> </body> </html> 日期控件转换成了table（绿色部分），下拉列表转换成了select标签（红色部分）等，所有的一切都转换成了浏览器能解释的html标记语言 没有什么特别的
2.下面是带有ScriptManager控件的例子
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head><title> </title></head> <body> <form name="form1" method="post" action="Default.aspx" id="form1"> <div> <input type="hidden" name="__EVENTTARGET" id="__EVENTTARGET" value="" /> <input type="hidden" name="__EVENTARGUMENT" id="__EVENTARGUMENT" value="" /> <input type="hidden" name="__LASTFOCUS" id="__LASTFOCUS" value="" /> <input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwUKLTkxMjIzNTI5NQ9kFgICAw9kFgICAw8QZGQWAWZkZJtbkkCYOre8ffrFCqW5LPWkPTtr" /> </div> <script type="text/javascript"> //<![CDATA[ var theForm = document.forms['form1']; if (!theForm) { theForm = document.form1; } function __doPostBack(eventTarget, eventArgument) { if (!theForm.onsubmit || (theForm.onsubmit() != false)) { theForm.__EVENTTARGET.value = eventTarget; theForm.__EVENTARGUMENT.value = eventArgument; theForm.submit(); } } //]]> </script> <div> <input type="hidden" name="__EVENTVALIDATION" id="__EVENTVALIDATION" value="/wEWMgLIi4jfDQLd2/zADgK38ereCQLa96nuBQLa94WJDQLa9/GkBgLa9+3fDwLa99l6Atr39cMFAtr34f4OApeUoIgLApeUnKMMApeUiN4FApeU5PkOApeU0JQGApeUzM8PApeUuGsCl5SUhggCl5TA7g4Cl5S8igYC8q3OkgEC8q26zgoC8q2W6QMC8q2ChAsC8q3+vwwC8q3q2gUC8q3G9Q4C8q2ykQYC8q3u+QQC8q3alAwC7brsvQ8C7brYWALturT0CQLtuqCvAQLtupzKCgLtuojlAwLtuuSACwLtutC7DALtuoyEAQLtuvi/CgLI04vIBQLI0+fjDgLI09OeBgLI08+5DwLI07tVAp3kj+UKAo2LpYsGApKLpYsGApOLpYsGApCLpYsGdr/l7ekdPMwRDZCnhQ2pPfOpOcI=" /> </div> <div> <SPAN style="COLOR: #ff0000"><SPAN style="COLOR: #339966"> <table id="Calendar1“>...</table> </SPAN> <select name="DropDownList1" onchange="javascript:setTimeout('__doPostBack(\'DropDownList1\',\'\')', 0)" id="DropDownList1"> <option selected="selected" value="0">==请选择==</option> <option value="1">Red</option> <option value="2">Yellow</option> <option value="3">Green</option> </select> </SPAN> </div> </form> </body> </html> <form id="form1" runat="server"> <div> <STRONG><SPAN style="COLOR: #ff0000"> <asp:ScriptManager ID="ScriptManager1" runat="server"> </asp:ScriptManager> </SPAN></STRONG> <asp:Calendar ID="Calendar1" runat="server"></asp:Calendar> <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="true" onselectedindexchanged="DropDownList1_SelectedIndexChanged"> <asp:ListItem Value="0">==请选择==</asp:ListItem> <asp:ListItem Value="1">Red</asp:ListItem> <asp:ListItem Value="2">Yellow</asp:ListItem> <asp:ListItem Value="3">Green</asp:ListItem> </asp:DropDownList> </div> </form>
没什么特别，只是添加了一个scriptManager,当然运行结果不会跟第一个实例有什么区别，因为页面内没有可以让ScriptManager局部更新的组件。
我们看一下服务器返回的html代码
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head><title> </title></head> <body> <form name="form1" method="post" action="Default.aspx" id="form1"> <div> <input type="hidden" name="__EVENTTARGET" id="__EVENTTARGET" value="" /> <input type="hidden" name="__EVENTARGUMENT" id="__EVENTARGUMENT" value="" /> <input type="hidden" name="__LASTFOCUS" id="__LASTFOCUS" value="" /> <input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwULLTE3MDQ3NDcyNDcPZBYCAgMPZBYCAgUPEGRkFgFmZGRJzKmEsYB5gVwYRx8dFV3x6MurTw==" /> </div> <script type="text/javascript"> //<![CDATA[ var theForm = document.forms['form1']; if (!theForm) { theForm = document.form1; } function __doPostBack(eventTarget, eventArgument) { if (!theForm.onsubmit || (theForm.onsubmit() != false)) { theForm.__EVENTTARGET.value = eventTarget; theForm.__EVENTARGUMENT.value = eventArgument; theForm.submit(); } } //]]> </script> <SPAN style="COLOR: #ff0000"><script src="/AJAX/WebResource.axd?d=WpudyoSACkhJZI41rIr6Gw2&t=634172191729687500" type="text/javascript"></script> <script src="/AJAX/ScriptResource.axd?d=BRDs2LbU_LAg6ZAoegBg0A1ZmMB4Gl-EP20pmeKgxP1i7fAhHRAcUfOQW96vJTq8YX82ufeV_8av8uEdGjhLBt36ynpIinbuj4reqRYgPiw1&t=5ccefe3d" type="text/javascript"></script> <script type="text/javascript"> //<![CDATA[ if (typeof(Sys) === 'undefined') throw new Error('ASP.NET Ajax 客户端框架未能加载。'); //]]> </script> <script src="/AJAX/ScriptResource.axd?d=BRDs2LbU_LAg6ZAoegBg0A1ZmMB4Gl-EP20pmeKgxP1i7fAhHRAcUfOQW96vJTq82Fnxq88VMyVxCirTmVquRfdErM4nM7jSYzP2oTAbs70SDfMUJ-ZIDBycHzaXmnVW0&t=5ccefe3d" type="text/javascript"></script> </SPAN><div> <input type="hidden" name="__EVENTVALIDATION" id="__EVENTVALIDATION" value="/wEWMgLGvacPAt3b/MAOArfx6t4JAtr3qe4FAtr3hYkNAtr38aQGAtr37d8PAtr32XoC2vf1wwUC2vfh/g4Cl5SgiAsCl5ScowwCl5SI3gUCl5Tk+Q4Cl5TQlAYCl5TMzw8Cl5S4awKXlJSGCAKXlMDuDgKXlLyKBgLyrc6SAQLyrbrOCgLyrZbpAwLyrYKECwLyrf6/DALyreraBQLyrcb1DgLyrbKRBgLyre75BALyrdqUDALtuuy9DwLtuthYAu26tPQJAu26oK8BAu26nMoKAu26iOUDAu265IALAu260LsMAu26jIQBAu26+L8KAsjTi8gFAsjT5+MOAsjT054GAsjTz7kPAsjTu1UCneSP5QoCjYuliwYCkouliwYCk4uliwYCkIuliwbzSm3y5GzwZploQy1UEn46DjrBBg==" /> </div> <SPAN style="COLOR: #ff0000"><SPAN style="COLOR: #000000"> <div> </SPAN> <script type="text/javascript"> //<![CDATA[ <STRONG>Sys.WebForms.PageRequestManager._initialize('ScriptManager1', document.getElementById('form1')); Sys.WebForms.PageRequestManager.getInstance()._updateControls([], [], [], 90); </STRONG>//]]> </script> </SPAN> <select name="DropDownList1" onchange="javascript:setTimeout('__doPostBack(\'DropDownList1\',\'\')', 0)" id="DropDownList1"> <option selected="selected" value="0">==请选择==</option> <option value="1">Red</option> <option value="2">Yellow</option> <option value="3">Green</option> </select> </div> <SPAN style="COLOR: #ff0000"><script type="text/javascript"> //<![CDATA[ Sys.Application.initialize(); //]]> </script> </SPAN></form> </body> </html>
相对于第一个实例，添加了一些js引用和一些js代码，尤其要注意加粗的地方，这里实际就是我们能实现刷新的重要部分。现在应该知道，为什么只有ScriptManager不能实现局部刷新了吧，因为在Sys.WebForms.PageRequestManager.getInstance()._updateControls([], [], [], 90)这句话中，没有可更新的控件。
可能到这里，还是不太相信添加这些代码就能实现局部刷新啦，我们继续往下看
3.带有ScriptManager和UpdatePanel控件的实例
<form id="form1" runat="server"> <div> <asp:ScriptManager ID="ScriptManager1" runat="server"> </asp:ScriptManager> <SPAN style="COLOR: #ff0000"><asp:UpdatePanel ID="UpdatePanel1" runat="server"> <ContentTemplate> </SPAN> <asp:Calendar ID="Calendar1" runat="server"></asp:Calendar> <asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="true" onselectedindexchanged="DropDownList1_SelectedIndexChanged"> <asp:ListItem Value="0">==请选择==</asp:ListItem> <asp:ListItem Value="1">Red</asp:ListItem> <asp:ListItem Value="2">Yellow</asp:ListItem> <asp:ListItem Value="3">Green</asp:ListItem> </asp:DropDownList> <SPAN style="COLOR: #ff0000"> </ContentTemplate> </asp:UpdatePanel> </SPAN> </div> </form>
这一步其实也没做什么，只是添加了UpdatePanel控件。
运行结果：
注意状态栏可是无刷新哦
看一下服务器端返回的html代码
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head><title> </title></head> <body> <form name="form1" method="post" action="Default.aspx" id="form1"> <div> <input type="hidden" name="__EVENTTARGET" id="__EVENTTARGET" value="" /> <input type="hidden" name="__EVENTARGUMENT" id="__EVENTARGUMENT" value="" /> <input type="hidden" name="__LASTFOCUS" id="__LASTFOCUS" value="" /> <input type="hidden" name="__VIEWSTATE" id="__VIEWSTATE" value="/wEPDwULLTE1OTA0NzEyNTMPZBYCAgMPZBYCAgMPZBYCZg9kFgICAw8QZGQWAWZkZNKOh9DNKQIiu+lJISv5z1xLDKNA" /> </div> <script type="text/javascript"> //<![CDATA[ var theForm = document.forms['form1']; if (!theForm) { theForm = document.form1; } function __doPostBack(eventTarget, eventArgument) { if (!theForm.onsubmit || (theForm.onsubmit() != false)) { theForm.__EVENTTARGET.value = eventTarget; theForm.__EVENTARGUMENT.value = eventArgument; theForm.submit(); } } //]]> </script> <script src="/AJAX/WebResource.axd?d=WpudyoSACkhJZI41rIr6Gw2&t=634172191729687500" type="text/javascript"></script> <script src="/AJAX/ScriptResource.axd?d=BRDs2LbU_LAg6ZAoegBg0A1ZmMB4Gl-EP20pmeKgxP1i7fAhHRAcUfOQW96vJTq8YX82ufeV_8av8uEdGjhLBt36ynpIinbuj4reqRYgPiw1&t=5ccefe3d" type="text/javascript"></script> <script type="text/javascript"> //<![CDATA[ if (typeof(Sys) === 'undefined') throw new Error('ASP.NET Ajax 客户端框架未能加载。'); //]]> </script> <script src="/AJAX/ScriptResource.axd?d=BRDs2LbU_LAg6ZAoegBg0A1ZmMB4Gl-EP20pmeKgxP1i7fAhHRAcUfOQW96vJTq82Fnxq88VMyVxCirTmVquRfdErM4nM7jSYzP2oTAbs70SDfMUJ-ZIDBycHzaXmnVW0&t=5ccefe3d" type="text/javascript"></script> <div> <input type="hidden" name="__EVENTVALIDATION" id="__EVENTVALIDATION" value="/wEWMgKmh4YaAt3b/MAOArfx6t4JAtr3qe4FAtr3hYkNAtr38aQGAtr37d8PAtr32XoC2vf1wwUC2vfh/g4Cl5SgiAsCl5ScowwCl5SI3gUCl5Tk+Q4Cl5TQlAYCl5TMzw8Cl5S4awKXlJSGCAKXlMDuDgKXlLyKBgLyrc6SAQLyrbrOCgLyrZbpAwLyrYKECwLyrf6/DALyreraBQLyrcb1DgLyrbKRBgLyre75BALyrdqUDALtuuy9DwLtuthYAu26tPQJAu26oK8BAu26nMoKAu26iOUDAu265IALAu260LsMAu26jIQBAu26+L8KAsjTi8gFAsjT5+MOAsjT054GAsjTz7kPAsjTu1UCneSP5QoCjYuliwYCkouliwYCk4uliwYCkIuliwYWM6Mt9LLccy445bZ7PABY3EeS5w==" /> </div> <div> <script type="text/javascript"> //<![CDATA[ Sys.WebForms.PageRequestManager._initialize('ScriptManager1', document.getElementById('form1')); <SPAN style="COLOR: #ff0000">Sys.WebForms.PageRequestManager.getInstance()._updateControls(['tUpdatePanel1'], [], [], 90); </SPAN>//]]> </script> <div id="UpdatePanel1"> <select name="DropDownList1" onchange="javascript:setTimeout('__doPostBack(\'DropDownList1\',\'\')', 0)" id="DropDownList1"> <option selected="selected" value="0">==请选择==</option> <option value="1">Red</option> <option value="2">Yellow</option> <option value="3">Green</option> </select> </div> </div> <script type="text/javascript"> //<![CDATA[ Sys.Application.initialize(); //]]> </script> </form> </body> </html>
相对于第二个实例的源码，我们可以看到差距是在红色的部分，多出了ScriptManager局部刷新的控件UpdatePanel1。
通过这三个实例呢，我们应该能够理解，为什么ScirptManager能够实现局部刷新了，关键还是引入了我们在源码中看到的js代码，真是这些代码实现了ScirptManager控件的局部刷新功能。
也可参考http://www.cnblogs.com/pangxiaoliang/archive/2009/06/28/1512758.html 写的也很详细，很不错。